"Rosie! Rosie wake up!" the boy hissed as he shook his sister awake.

"Seb what do you want?" the young girl groaned back. "Go to sleep!"

"But Mummy is kissing Santa!" Seb whispered. And suddenly, Rosie was wide awake she sat up and peered at her brother in the darkness.

"Really?"

"Yeah, come on!" he grabbed his sister's hand and the two scampered from Rosie's bedroom. They crept down the stairs together and peered through the gap in the doorway into the living room. "See!" Seb pointed and Rosie looked. Then she frowned.

"That's not Santa! Santa wears red, not black," she whispered to her brother.

"But he comes down the chimney though, doesn't he?" Seb replied, rolling his eyes. "He's covered in soot!"

"Oh…" Rosie went back to looking at the soot covered Santa. "Why does he have weird ears then? They look like the ones I wore at Halloween. Like cat ones." Seb frowned at her question, but as the older sibling, he was determined to find the answer.

"Maybe they help him listen for intruders?" he suggested weakly.

"Yeah maybe," Rosie agreed. "So why is Mummy kissing him?"

"To thank him for our presents!" Seb answered this question at once. "Like when Grandma kisses Grandpa for bringing her cups of her smelly tea!"

"But Grandma only does that to Grandpa," Rosie countered.

"'Cos Grandpa is the only one that gives her tea," Seb whispered. "Shh, look!"

Their mother and Santa had broken apart.

"I missed you, Princess," Santa said in a gentle voice.

"It's been too long," their mother agreed.

"Did you hear that?" Rosie squeaked. "Santa called Mummy a princess!"

"How long will you be here, Chat?"

"For as long as you want," he replied. Rosie and Seb watched in awe as their mother stepped back slightly. "My other life's commitments have changed. I'm moving back to Paris."

"Does this mean…?"

Rosie frowned, it sounded like her mother was going to cry, but she also sounded happy. Grown ups were weird.

"Yes," Santa said with a grin like a cheshire cat. Then the focus of his eyes changed slightly. Seb and Rosie squeaked in unison and flattened themselves against the wall, so Santa wouldn't spot them.

"Seb," Rosie whispered. "Why does Santa have a tail?"

"Shh, if he catches us, then he'll think we're naughty and take away our presents!"

Rosie clamped her mouth shut.

"Princess, the kittens are listening," they heard Santa say.

"Kittens?" Seb mouthed at Rosie, but she just frowned back.

They heard their mother give an exasperated sigh.

"Sebastian! Rosemarie! Come here!" she called. "Don't even think about running back to bed."

Shame faced, Seb and Rosie shuffled into the living room. Neither of them could make eye contact with their mother or Santa.

"Why aren't you two asleep?" their mother began. Neither of them answered. "You know if you don't sleep on Christmas Eve, Santa Claws doesn't come."

"Isn't he Santa Claws?" Rosie asked. Their mother glanced at the man they thought was Santa and laughed.

"Santa Claws?" not-Santa said. "Santa Paws more like." Their mother batted not-Santa on the chest.

"You're dreadful," she muttered before turning back to her children. "No, this is not Santa. This is Chat Noir."

Rosie and Seb's mouth's dropped open.

"The real Chat Noir? Where's Ladybug then?" Seb asked as soon as he'd recovered.

"Why were you kissing Mummy?" Rosie asked.

"Why wouldn't I want to kiss someone as wonderful as your mother?" Chat replied. "And Ladybug is off somewhere living her own life."

"You don't know where she is?"

"I don't even know who she is under her mask!" Chat said, still smiling. "She keeps her identity a secret."

"Even from you?" Rosie asked, amazed.

"Especially from me," he told her with a slight frown.

"Now you two should be asleep," their mother said warningly. "Otherwise the real Santa won't come."

"But I wanna play with Chat Noir!" Seb whined. "I wanna hear about all his adventures with Ladybug!"

"Yeah!" Rosie joined in.

"Yeah!" Chat said, smirking at their mother. "I wanna play with my kittens!"

Their mother scowled.

"Tomorrow," she said. "Chat can come back tomorrow and you can all play to your hearts content, but now, you're all going to bed."

"But Mum!" Seb complained.

"Unless you'd rather he just didn't come back?" The two children grumbled and turned to head back to their bedrooms. "I'll be up in a minute to tuck you both in."

Seb led the way up the stairs, but before turning into his bedroom, he grabbed Rosie by the arm.

"I think I know who Chat is," he whispered, switching to Chinese as they always did when talking about a secret.

"Who?" Rosie asked in wonder.

"I think he's our Dad."

But before Rosie could reply, they heard their mother coming up the stairs and so they scampered into their beds.

As her parents were in China visiting relatives, Marinette had taken up Alya's offer of Christmas lunch together. Once her children had opened all of their presents, she wrapped them up and together walked hand in hand to Alya and Nino's place.

She vaguely knew her two rascals were up to something, mostly because they kept muttering in Chinese to each other, which they only did when they were up to something and had seemingly forgotten that she could understand every word they said. She suspected their muttering today had something to do with Chat.

Chat.

Chat was returning to Paris after his real life had taken him away from her for so long. They'd made a deal, all those years ago, that he would only reveal himself to her when he knew he was going to be back in Paris to protect her and their children. Of course, he didn't know she was Ladybug and thus perfectly capable of defending them herself, but still, it had made sense. It was less risky that way. And once he revealed himself, she would do the same.

Seb ran ahead to knock on the door and by the time Marinette and Rosie had caught up, Nino was already at the door.

"Hey," he greeted them. "Food is almost ready and Adrien's here."

"Who's Adrien?" Seb asked.

"The guy your mum used to fancy at school," Nino replied with a smirk at the scowl adorning Marinette's face. The little family entered and took off their shoes.

"How's Alya?" Marinette asked to change the subject.

"Fit to burst," Nino said with a laugh. "Almost like someone put a giant bubble in her stomach." He winked at Marinette, who groaned at the lame joke.

"Does this mean Auntie Alya still won't play with us?" Rosie asked.

"Yeah, not today, but you can play with Adrien."

They followed him to the lounge, where a heavily pregnant Alya was lounging on the sofa and Adrien Agreste was chatting with her.

"Rosie! Seb!" Alya attempted to move, but gave up as the two children jumped to embrace their makeshift aunt.

"When is the baby going to hatch?" Seb asked. Marinette hid a smile behind her hand at his use of language. After Alya had become pregnant, she found herself being inundated with questions about where babies came from. As a result, she ended up taking her children to a farm and showing them chickens and their eggs. She had explained that chickens put everything needed to make a baby in the egg, then it grows in the egg and hatches when ready. She'd gone on to say that humans keep their eggs in mummys' tummies so they don't lose them.

"Soon," Alya said, smiling.

"Adrien," Marinette greeted him politely. "It's good to see you."

"It's Dr Agreste now," Nino teased.

"You completed your PhD?"

"Yeah, had a few issues getting it done and had to take some time out, but I passed the viva a month ago," Adrien said with his easy model smile.

"Kids, why don't you go and show Adrien the baby's room?" Nino suggested.

"Yeah!" the two children latched onto Adrien and dragged him away.

"I'm going to go and finish the food," Nino said and disappeared.

Marinette took a seat and looked expectantly at Alya, she knew her friend was bursting to say something.

"You know, your kids look awfully like Adrien," Alya said slyly.

"Their father was blond too," Marinette said evasively. She had not told Alya the truth of their parentage, other than they had the same father. Marinette did not like keeping things from her friend, but considering she didn't technically know the identity of their father, it wasn't like Alya was missing out on too much. Plus if she'd said she'd slept with Chat Noir, she imagined Alya would want a very detailed interview for her Ladyblog followed by discussions of what that meant for the Ladybug - Chat Noir dynamic and exactly how good Chat was in bed. That was definitely best avoided.

"So you just have a thing for blonds, huh?"

"Please Alya," Marinette begged for her friend not to continue and Alya relented.

"So did they like their presents?" Alya asked and Marinette jumped on the topic.

Meanwhile, Adrien was concerned. The two children had dragged him about the house and had been muttering in Chinese. He'd only managed to discern a few of their words and silently cursed himself for not practicing his language skills. Despite this, he had definitely heard the word 'cat'.

Fortunately, Nino rescued him and soon they were all eating Christmas dinner. Adrien found himself watching Marinette out of the corner of his eye. Alya caught him doing this and smirked, so he looked away. Thankfully the boy, Seb, provided a distraction in the form of asking him questions.

"What do you do?"

"I'm a physicist," Adrien said, then reminded himself he was talking to a six year old. "A type of scientist."

"Cool, do you do about planets and stuff? Planets are cool!"

"Not quite, I look at things at the other end of the size scale. I study things that are really small."

"Like peas?" Seb asked with an innocent frown.

"Smaller than peas!"

He smiled as the boy tried to think of something smaller.

"Like the little beads Mummy uses in her designing?"

"Smaller than that!"

"But they are tiny!" Seb sounded shocked that there could be anything smaller.

"Yeah, and my newest project is going to be looking at a potential source of dark matter." He stopped himself before adding 'in Chat Noir's catastrophe magic' because he suspected the children might not keep quiet about the incident the previous night. At the deep frown that appeared on Seb's face, Adrien immediately wished he hadn't spoken, because he knew what the next question would be, and knew he had little way of answering it in terms and six year old could understand.

"What's dark matter?"

"Seb, you need to learn a lot more in science before you learn about dark matter," Marinette chimed in. "Adrien has been to university, and done a doctorate in physics to learn about it. So you're going to have to study hard if you really wanna know the answer to that question."

"But I wanna know now!"

Adrien shot a grateful look at Marinette, but she didn't see it, she'd already turned her attention back to Alya and Rosie's discussion on baby names.

The evening could not come soon enough for the children, they had hatched their plan and we're waiting ready. Little did they know that Lady Luck was on their side.

Only five minutes after Chat had arrived, their mother received a phone call.

"Nino? What is it? What! Really? I'll be right there!" Their mother turned to them and said very seriously that Auntie Alya was hatching her baby.

"Why didn't she do it earlier?" Seb asked. "We could have watched!"

He missed his mother's look of exasperation.

"Chat, can you watch them?"

"Of course Princess," Chat replied.

"Let's put a film on," she suggested, knowing it would keep her children quiet. Once she'd set up a DVD, she grabbed her keys and phone and ran out of the door.

"Blanket fort!" Seb declared, and with seemingly well practiced haste, the two children bounded away and returned moments later with every duvet, blanket and cushion in the house.

Chat couldn't help but laugh as they constructed the 'fort', which was more of a nest really. His kittens looked so happy about something as simple as a few blankets. But then again, it wasn't like he would turn down something warm and comfortable either.

A few minutes after they started watching the childrens' favourite Disney film - Mulan, of course - Rosie raised a few questions.

"Chat, do you love Mummy?"

"Yes, I do."

"And Mummy loves you?"

"Yes, I think she does," he replied tentatively, scared where her questions were leading.

"Does that make you our Daddy?"

Chat felt Seb look around too and both children waited for his answer. He and Marinette were going to tell them together. But he could not lie to his kittens.

"Yes, it does."

And they were off in rapid Chinese again. But the tone of Seb's voice was very much 'I told you so'.

They did not ask any other questions, but continued watching the film. This surprised Chat, who expected them to question why he hadn't met them before. Obviously they had accepted his superhero status as reason enough.

The doctors said that the birth was one of the quickest they'd ever seen. For which Marinette was supremely grateful and not particularly surprised; Alya had been eager to give birth already for the past fortnight. But it meant she could get back to her own children while Alya and Nino argued over the name of their daughter; they still hadn't agreed though Marinette had her bets placed on Alya.

Yet as she approached her house, she could feel something was wrong. The sounds coming from it sounded like someone was being murdered. Marinette immediately called upon Tikki and transformed as she rounded the back of the house.

Someone had found Chat, she thought, someone had found Chat and they must be fighting. But how had they found Chat? Were her babies okay?

She entered through the back door, yo-yo ready to strike whoever had made the foolish mistake to try and hurt her family.

When she got to the lounge though, she realised it had very much been a false alarm. But it was too late, as Ladybug studied the scene before her - which consisted of Chat on his stomach with his arms and legs tied together with his own tail and her children climbing on top of him - they all looked round to stare at her.

"Ladybug!" Seb said in amazement.

"My Lady!" Chat said with a mixture of astonishment and pleading.

"Mummy!" Rosie cried with glee and she bound off of Chat and ran to hug Ladybug's leg.

They all looked at Rosie. But Seb recovered quickest and used Chat's distraction to finally prize the ring off of his finger. His transformation released.

"Adrien!" Ladybug stammered in shock.

"I told you he looked like Chat!" Seb hissed to Rosie.

Adrien, now free of the tail tying him up, scrambled into a sitting position.

"My Lady, I'm sorry," he said quickly. Though Ladybug was still in shock, she knew what she had to do. She released her own transformation and it was Adrien's turn to let his jaw drop.

"Princess!"

"Told you!" Rosie hissed back at Seb.

"It was you," the two adults said in unison.

"All this time?" Marinette continued.

"And you never told me!" Adrien finished.

They stared at each other for a minute. Then both burst out laughing.

Marinette woke the following morning with her three favourite people surrounding her. They had never left the blanket fort that had been constructed, but had watched films and played games until one by one, they'd fallen asleep.

"Mummy?" a small voice whispered. Marinette looked around at her daughter, who was leaning on Chat's - Adrien's - leg as a pillow. "Will Chat stay forever now?"

"Would you like him too?" she asked back.

"Yeah," the little girl whispered. "And I promise to keep it a secret that you're Ladybug too!"

"Good," Marinette said. She couldn't really move, as Seb was using her as a pillow. But Rosie spoke up again.

"You're a bit like Mulan huh?"

"How so?"

"You both dress up as something you're not and save people!"

Marinette saw the glee on her daughter's face and couldn't bring herself to mention several other superheros that came to mind that did exactly the same thing.

"Yeah," she said quietly. "I guess I am."

Rosie grinned and closed her eyes.

"This is the best Christmas ever," she whispered.

Author's note: So this was also AmyNChan's fault. But I had fun writing it so ah well! Please review :)