A/N: I saw this post going around Tumblr about boys and being weirded out about period stuff. And I figured with four girls in that house, it would be perfect prompt for my Castle family.

Enjoy!

"I need help!" Castle calls into the house. He drops his arm full of grocery bags onto the kitchen counters and heads back out to the car for another.

Liam comes into the kitchen a second later and starts to unpack the bags and set their contents onto the counter to be put away. He silently cheers when he finds his dad bought the 'good kind' of lunch meat. Danielle and Miyana are not far behind and join their brother to help. They work together, pausing only when their dad brings in another load, dancing around each other in a well-rehearsed ballet around their kitchen.

Everything is going fine until Liam calls out and tosses the bag he was holding onto the counter, the box inside thunks against the granite.

"What?"

"What's wrong?" His sisters ask, concerned.

Liam's hands are held to the sky, a look of terror and disgust on his face. "Nope. Nope," he simply says.

"What?" Danielle asks, going over to the bag her brother had thrown. "Oh my god! Really, Liam?" She asks, pulling out a new box of tampons out of the bag. "Grow up."

"Oh, good!" Miyana cheers. "I didn't think dad saw them on the list. I needed some."

"Those are disgusting! Put them somewhere out of the way," Liam tells her, completely put off by the box his sister holds.

"Oh come on! There's nothing bad about them. It's a new box, they're clean, relax," Miyana laughs, taking the box. "Are you scared?" She waves it in front of her brother's face and laughs as he jumps back further, holding out his hands to block himself from the evil tampons.

"Stop it, Mia!" Liam calls, and at that second Castle comes in, throwing a curious glance their way.

"Stop what?"

"Dad! They're being mean to me!" Liam whines, like when they were little.

"No, we're not!" Danielle defends.

"Then what are you doing?"

"Making him squirm," Mia grins, waving the box again and laughing as her brother cringes.

"Stop that!" Castle orders, snatching the box out of his daughter's hand.

"Come on, Dad! It's funny!" the girls laugh.

Castle takes stock of the situation and studies the package, and after a minute, smiles.

"It's not funny!" Liam shouts at his dad's reaction. "It's gross."

"Bro," Castle starts, turning to his son. "You live with four girls, you have to know that they need things like this."

"I know. But they're gross! I mean-"

"What, Liam? What do you mean?" Miyana asks, sitting on one of her hips, crossing her arms over her chest.

"Well. . . I. . I just mean they are gross and I don't even want to know what goes on to need those."

"They are for our period. You remember that from Sex Ed, right? It's when the lining of a woman's uter-"

But Miyana's voice is drowned out as her brother shouts and dashes from the room. The girls laugh, amazed at how immature their brother can be.

Castle just shakes his head, setting the box of tampons onto the counter. "Will you guys finish putting this stuff away?"

"Yeah."

"We got this," the girls reply.

"Good. And don't terrorize your brother, okay? I know it's funny, but he doesn't like it."

"Okay," Danielle answers, sharing a mischievous look with her sister.

"I'm serious, girls," Castle says.

"Okay!" Danielle insists.

And while the girls finish putting away the groceries, Castle heads upstairs to make sure his emotionally scarred son is alright.