"You're WHAT?!" Percy exclaims.

"I'm pregnant! A little sister or brother," says Sally kindly. "You're going to be a big brother!"

"But why?!"

Annabeth jabs him in the ribs with her elbow. "You don't ask your mother why you're getting a new sibling, you jerk," she snaps quietly.

"No, it's okay," laughs Paul. "I get it. I was the only for a while too. Gets under your skin when a new one comes along."

"Nothing is under my skin," says Percy. "I'm just, I mean, how?!"

He gets identical eye rolls from his mother and girlfriend and hysterical laughter from his step father.

"Shut up," he grumbles, his face feeling bright red. "Oh my gods, shut up right now."

"How?!" chortles Paul. "Percy, man, you're a senior in high school. My high school. I'm not giving you any explanations."

"That's not what I meant!" Percy exclaims, but even he can't blame the blush on his cheeks on the Christmas lights shining from the tree. "This is the weirdest Christmas Eve ever."

"When did you find out?" Annabeth asks. Percy's relieved – all the questions he wants to ask are a little bit stuck in his head and she, like always, has his back while he babbles inappropriately. Some things never change.

"A little while ago," Sally replies. "But we didn't want to say anything until we were sure it could happen. I'm five months along, so it seems we should be alright now though I am older, so the pregnancy might be high risk toward the end."

Percy feels a wave of fear cover him as he thinks about what the hell "high risk pregnancy" means. He knows about babies and shit – he, unfortunately, didn't miss the semester where he had to take Health – but he's got no idea about what high risk pregnancy was.

His response to his mother is, "But baby?"

"I'll take him for a walk to the library," says Annabeth, pulling on Percy's arm. "We'll do that first before dinner so he doesn't explode."

He lets Annabeth pull him out the door, and waits until they're on the sidewalk and on their way before he says it.

But he can't quite get the words out. Instead, he just turns to her, sure he looks befuddled, and says, "Baby?"

Annabeth snorts. "Your mom isn't old, Percy. She only had you at eighteen, right?"

Percy shrugs. "Yeah. So?"

"So she's having a second one when a lot of people have their first. You're not going to freak out about no longer being an only on either side of the parents, are you?"

He shrugs. "Maybe I will."

Annabeth rolls her eyes. "You, Percy, are twelve."

"I'm also apparently going to be an older brother."

The next Christmas Eve, his little brother Liam is camped out on Percy's lap, almost entirely asleep. Percy's not far from napland either.

In what could either be two minutes or two hours, he feels someone's lips press against his temple.

"Percy," the voice singsongs, "it's time to get up, unless you want to skip the library this year."

His eyes slowly flutter open. Annabeth has a hand on Liam's fuzzy red head, brushing his soft hair back. "Morning, sleepy face," she says with a smile.

He slowly sits up from where he had been lying on the couch, careful to keep the eight month old munchkin from being jostled. He was a hellion today – the longer he sleeps, the better.

"Morning," Percy says. He returns Annabeth's smile. "Babysitting is hard."

"I guessed," she giggles. "You were out cold for ages. Your mom and I have been chatting in the kitchen for the past three hours."

"Three hours?!" Percy exclaims, and Liam squirms on his chest, making quiet muttering sounds. Without a second thought, Percy lets Liam suck on his finger and the baby quiets in seconds. "Shoot," mutters Percy. "Didn't mean to wake him up."

"He looks content now," says Annabeth. Then her eyes light up. Percy waits for her to explain what that look means. "What do you think of shifting our library plans and bringing Liam with?"

"You think it'll work?" Percy asks, shifting enough to stand with Liam securely resting against his shoulder. "You think he'll be quiet enough?"

Annabeth shrugs. "Your mom needs a nap and we were going to go to the library anyway. Why not give your mom some Christmas time alone with Paul?"

Liam lifts his head and looks right at Annabeth until he reaches his little arms out for her.

"I think your brother likes my idea," Annabeth chuckles as she takes him in her arms. "What do you say, Little Man? Wanna go play with books?"

Liam giggles and smiles.

"I think that's a yes," says Percy. "Come on. Let's go get our book on." As Annabeth turns away, Percy whispers in his brother's ear, "I know you two aren't related, but inherit her brains!"

Annabeth just chuckles.