spark. (n) 1. a glowing bit of matter, especially one thrown off by a fire; 2. anything that activates or stimulates; inspiration or catalyst.

"It will be all right, Zuko."

That seemed to be Katara's constant refrain these days. Zuko knew she was probably tired of his fretting—no, he knew without a doubt that she was, because on one of the days when the pregnancy hormones had gotten the better of her, she'd hurled the leftover water from the children's bath in a small water whip that had stung before soaking his tunic and had told him to stop worrying because there's nothing we can do about it anyway and you're driving us all crazy with your nonsense.

He hoped that wasn't strictly true; he hoped the children hadn't detected that he was worried, especially because it concerned them. He was pretty sure they didn't know, though—Kenzo was three and didn't know the right questions to ask; Kya was two and didn't know what bending was beyond the fact that daddy could make fire in his hands to calm her fears on dark nights and mama could make pretty shapes with the water in her bath.

Katara knew, though, and, excepting the bathwater incident, she did her best to be understanding. She would never completely understand his fears when it came to the children, how he would sometimes wonder if they had done the right thing by having children at all, no matter how much he loved them, because he was still haunted by the ghosts of his past that whispered that his choice to fight on the side of right was not final, that he could yet become his father—but it was the times when he was weakest that she wrapped him in her arms, held him close, and whispered fiercely that he was a good man and that she would not let him change for the worse, ever.

Her words reassured him, because even if he couldn't always trust himself, he could trust Katara.

Each new pregnancy assuaged his fears slightly—when Katara had told him this third time that she was expecting, the joy came much more quickly than before on the heels of his initial panic. But their children were still young and he heard the question whispered everywhere in court, not just in his own mind: what would they bend? He had known going into marriage with Katara that their children would likely be a mix of firebenders and waterbenders. He also knew that it was a big risk to take because having a waterbender as the heir to the Fire Nation throne would threaten the barely stable peace of his country. Even Katara, for all her national pride, was prudent enough to recognize that there was a danger of revolt if their firstborn, Kenzo, turned out to be a waterbender.

As much as Zuko recognized the weighty responsibility of raising a bender of any kind and of teaching his children to use their power responsibly, he hoped that at least one of their children—preferably Kenzo, since he was first in line for the throne—bent fire. That was part of the reason he had suggested this summer trip to Ember Island. Kenzo was three now and should start exhibiting signs of bending soon. Zuko thought that perhaps a few weeks spent outdoors in sunshine and heat would encourage those first sparks of fire, if they were indeed to come.

They had been here on Ember Island for two weeks now with no results other than that Kenzo and Kya thoroughly enjoyed building sandcastles and splashing in the waves while Katara and Zuko faced the reality that, even though they'd convinced themselves this vacation was going to be relaxing, they were more exhausted than ever after spending days spent chasing two toddlers around the beach.

Sometimes late at night and early in the morning, while the children still slept, Zuko would wander the halls of the house the way he did every time they visited here. The years after the war had brought much healing—especially with Katara's help, for he had found that she had the ability to heal so much more in him than just his physical wounds—but trips to Ember Island, as much as he enjoyed them, always brought back unwelcome memories along with the good ones.

Whenever Katara awoke to find that he had left their bed, she would come and join him quietly, walking beside him and taking his hand in hers. He had told her once that the past seemed easier to bear when she was nearby. She had told him that that was because she and the children represented his future.

At this very moment, one part of his future was about to smash the other's sandcastle, though, so he rose from where he had been lying next to Katara, who had fallen asleep on a blanket, to intervene.

"Kenzo," he said, gathering the three-year-old up in his arms and spinning him around. "Please don't step on your sister's sandcastle. Would you like it if she broke your things?"

Kenzo frowned and protested, "She did. Kya did break my sandcastle yesterday. She stepped on it and it went away in the waves."

Zuko sighed and kissed his son's forehead. "And mama and daddy talked to Kya about treating other people's things respectfully, just like I'm talking to you now. You're the big brother, so you need to show her how to be good."

Kenzo nodded. "I do that," he said solemnly.

Zuko smiled. "That's my boy," he said, putting his son back down. "Now why don't you build a sandcastle next to your sister's?"

"Okay," Kenzo agreed.

Kya stood up and toddled through the sand to grab her father's leg. "Hug daddy!" she said.

He reached down and scooped his daughter up in his arms, too. She flung her arms around his neck and said, "Cuddle daddy." The sentiment only lasted for a few seconds, because sandcastles were much more interesting than her father in her two-year-old mind, and when he set her down again, she joined her brother in the sand building castles that looked more like lumps than fortresses. They were happy, though, and proud of themselves.

Zuko took advantage of the temporary calm to rejoin Katara on the blanket, draping an arm over her sleeping form and propping up his head on his other arm so that he could keep an eye on the children.

This was what he remembered, he thought, from his earliest days at Ember Island. He remembered family trips to the beach back when his family was whole, before the war and his father's grasping for power had torn them apart. So much had changed since then, so much of the world had been destroyed and reshaped. For a moment, he squinted up at the bright sun that shone overhead. This was a new start, he realized. The cycle had come around again and now it was up to him and to his family not to repeat their parents' mistakes.

Zuko's musings were interrupted by a screech from Kenzo. "DADDY! Kya burneded my CASTLE!"

The cry woke Katara and both parents scrambled to get to their children quickly. With the advantage of having been awake already, Zuko got there first and pulled both children into his arms as he and Katara looked between the steaming pile of wet sand and each other in shock. Katara's eyes were wide as she knelt down next to Kya and took her from Zuko.

"Kya," she said seriously, looking her daughter in the eye. "Did you burn Kenzo's castle?"

Kya smiled sweetly. "Fire!" she proclaimed. "I make fire like daddy!"

At that, Kenzo twisted in Zuko's arms and frowned. "I can make some fire like you, Daddy, too," he said, holding out his hand and mimicking a firebending move. To Zuko's astonishment, a small flame appeared over his son's hand. "But Kya burneded my castle," he continued, pouting.

Zuko helped Kenzo make the motion that would direct the flame in his hand toward the waves, where it fizzled in a burst of steam. Not sure how much he could trust his voice, Zuko managed to say, "Let's go home."

He picked up Kenzo, Katara picked up Kya, and the four of them gathered their things to head inside for the rest of the day. They could lecture about not burning your sibling's sandcastles later.

As they walked toward the house, Zuko and Katara exchanged glances over the children's heads. Zuko could feel his stomach roiling with mixed relief and anxiety. Firebenders: their first two children were firebenders. That was good news for political stability, but he was reminded once again of the need to teach their—young, so very young—children about the great responsibility that came with bending any element. And Kya was young, too young—she shouldn't be bending yet. Bending at this age meant that she was a…prodigy. The word thudded in his heart, rattled through his frame. Like Azula.

He looked up at Katara as she shifted Kya in her arms, around her pregnant belly that was obvious but not yet uncomfortable, and when she met his gaze, he knew she was thinking the same thing. Nonetheless, she smiled, a smile that calmed him despite the nervousness he saw in her eyes. He could almost hear her voice: It will be all right, Zuko.

Later that night, after they had talked to the children before bedtime about what it meant to be a bender, after they had sent a messenger hawk to the capital so that a firebending tutor would be waiting for them when they returned, after they had gotten over the initial shock and talked things over between the two of them, had begun to wrap their minds around the concept of raising firebenders, and then had wrapped their limbs around each other in the ancient union of lovers, Katara rolled onto her back, laced her fingers over her growing belly, and looked over at Zuko as she said softly, "This one's a girl and she's going to be a waterbender."

Zuko didn't know how much of his wife's statement was certainty and how much was conjecture, especially given that she'd been as shocked as he had been when their first two children had begun firebending on the same day, but he leaned over and kissed her anyway.

It wasn't until three years later, on another summer trip to Ember Island, that third-born Ursa proved her mother right when she drew up an awkward wave and destroyed yet another of Kenzo's sandcastles.