*A/N: Prompt from Shutterbug5269: "Alexis and Kate give birth on the same day? (Sorry...I have babies on the brain) Kate was due two weeks later…but baby came early."

Must Be The Genes

It was supposed to have been a joke, just something said in the moment to make him squirm. She hadn't really meant it. She hadn't intended for it to happen. He knew that. Yet, four years later, it was happening.

Castle paced back and forth down the hospital corridor, feeling lost, uncertain where he should be. This was a decision he never thought he'd have to make. Two nurses rush past him and entered the room on the left, and his heart wavered with worry. That couldn't be a good thing, right? He moved a foot in that direction, but then stopped when the scream from the room on the right met his ears as the door pushed open and his mother appeared, looking at him with an annoyed expression.

"Richard, it's almost time. You need to be in here… now!" she declared forcibly, gesturing with a dramatic wave of her hand.

"But… but…," he turned his head and looked longingly at the room on the left.

"Don't worry about her. Harry's with her, she's fine," Martha assured him, motioning him into the room. He went willingly, unable to resist the magnetic pull. He couldn't really keep himself away for that long. It was amazing he'd lasted as long as he had. And besides, his mother was right, Alexis would be fine. Harry was with her.

Slipping into the room, another scream bellowed out from the woman on the bed, and Castle, done wasting time, rushed to her side. He grabbed her shaking hand, and her grip was fierce, nearly cutting off all blood flow into his fingers. He bent down and pressed a reassuring kiss to her forehead as he brushed stray strands of brunette hair away from her sweat slick brow.

"I'm here," he said, voice wavering with raw emotion, both in awe and apology. "I'm here now. I'm sorry… I'm so sorry I took so long… I… I just couldn't decide."

"I understand, babe," Kate wheezed out between breaths, chest heaving. "She's your little girl."

"But you're my wife," Castle argued, disappointed with himself. "I should've been in here with you long before now. And as Mother pointed out, Alexis has Harry."

"I'm sorry too, for what's it worth," she said. "I thought I had another two weeks."

"Don't apologize, honey," Castle said. "It's not your fault. You've been extraordinary this whole time."

"Well I don't particularly feel extraordinary right now," Kate grumbled, gritting her teeth as another contraction hit her. The labor had not been kind to her, and the guilt at having not been at her side for most of it, supporting her as he had throughout the entire pregnancy, began eating him up. After the contraction past, Kate squeezed his hand. "She's in a good hands, Castle," she reassured him. "Harry's a good man."

Castle's heart clenched almost painfully in his chest. Here Kate was struggling with some intense labor pains, and she was the one taking the time to comfort him over his silly grief at not being in the room with his daughter as she gave birth to his first grandchild.

"Oh, Kate," he shook his head, shamefaced. "I really don't deserve you."

"Silly man," she grinned through the pains, beckoning him too her with her eyes.

He could do little but obey her silent command. Bending down, he pressed his lips to hers in a soft kiss. "I love you, Kate, so much," Castle asserted in a voice just loud enough for only her to hear.

"I love you, too, Rick," Kate hummed in appreciation, smiling up at him, giving his lips one final nip before resting her head back against the pillow. "And I'm better now that you're here."

He nodded, before then glancing over at the doctor, who was seated between Kate's opened legs, checking her progress. The woman gave him a nod. Turning his attention back to his amazing wife, Castle accepted a damp washcloth from a nurse, and dabbed it against Kate's forehead. He leaned down and kissed her once more. "You're doing great, Kate. Almost time."

Kate inclined her head, gritting her teeth. "I'm ready."


"You did great, Kate," Castle said, gently carding his fingers through her hair as he gazed down at their little bundle of joy—Alexander James, AJ for short. "I've said it before, and I'll say it again… you're extraordinary."

Kate bit her lower lip and shook her head, almost bashful. "Oh, Castle… stop, you'll embarrass me," she declared. "I must look a mess."

"No. Not at all. You're glowing," he assured her. "You're more beautiful now than I can ever remember."

"So you're saying I wasn't beautiful before?" Her nose scrunched up as she narrowed her brows, gracing him with a watered-down version of her famous glare.

"What? No… no way, come on, Kate… you… um… you know what I meant," he stammered out, squirming under her stare, as he always did.

"Since I just gave birth to our son, I'll let you off with a warning," she asserted with a smirk. Her eyes flashed with mirth. "God, Castle… you're so easy."

He shook his head at her, before silencing any more of her teasing with a kiss. Castle turned his attention back to the small bundle in her arms. "He's perfect," he proclaimed.

"Yeah, he is," Kate agreed on a sigh. "He's got your eyes."

"And your nose."

"And your chin."

"Poor little guy," Castle smirked, gently running his fingers along his son's cute little chubby cheeks, smiling when his tiny eyes blinked open and he nuzzled into his father's touch.

The nurses had just finished cleaning Kate and disposing of the afterbirth, when someone knocked at the door. Martha all teary-eyed and happy rushed to open it. Jim appeared, and Kate smiled up at her dad as he came over to get a look at his grandson. Castle stepped back and watched the exchange.

"Oh, God… Katie, he's gorgeous!" Jim exclaimed, gently running his fingers through the little tyke's mass of brown hair. The older man's eyes grew watery, and he bent down to give his daughter a kiss on the cheek.

Martha took the opportunity to excuse herself, saying she wanted to check on her granddaughter. Castle nodded, telling her it was all right, part of him wishing he could go with her and make sure his little girl was doing okay. From what little he'd heard from the nurses, Alexis's childbirth hadn't been easy and in the end they had to do a c-section. But he held back, staying where he belonged, by his wife's side.

Jim turned to Castle and shook his hand, before pulling him into a fatherly hug, slapping his back. "Thank you, Rick," he said. "I'm so very grateful my Katie found you… or should I say, you found her?" He chuckled and shook his head, wiping at his eyes… happy tears.

Kate laughed, "More like he wouldn't stop following me around." Her eyes softened, though, as her gazed drifted over to Castle. "But yes, I'm glad he didn't give up."

"Not like you made it easy," Castle defended himself with a smirk. "I should get some sort of medal."

"How about a son? Would you take that?" Kate teased.

Castle smiled, slipping an arm around her shoulder as he pressed a kiss to her smiling lips. "In a heartbeat. From you—with you—Always. I'd do it all over again just to be here with you."

"Oh, Rick," Kate gave him a watery smile. "You big softy."

"He's a romantic at heart," Martha declared, standing beside Jim. "He gets that from me. You're welcome!"

Another knock came from the door, and Jim raised a hand to block Castle, halting him in his tracks. "Stay with your wife, son, I'll get it."

"You heard that," Castle crooned as he slipped back next to Kate, primping like a strutting peacock. "He called me son."

"Yeah, I heard," Kate beamed up at him. "And it's the truth, Rick. We're all family. Even before we finally got married."

"I love you," he said, unable to take his eyes off his gorgeous wife and their newborn son.

"I love you, too, babe," Kate smiled up at him as he leaned down and kissed her.

A throat clearing interrupted them and they both parted, blushing slightly at having been caught. Kate kept her eyes avert, her cheeks flushing an adorable shade of pink, as Castle looked up to see with pleasant delight that Harry had appeared, carrying a small bundle wrapped in a blue cloth. Castle grinned as his son-in-law stepped through the doorway. Turning back to Kate, he leaned down and brushed his lips across the shell of her ear.

"I think AJ's nephew wants to say hi," he said softly. Her hazel eyes snapped up and she offered Harry a smile as the younger man approached with their first grandchild.

"How's Alexis doing?" Kate asked first.

"Good, she needed some rest, so I thought it would be nice to introduce you guys to your grandson," Harry said. Castle moved aside as he held out the small bundle towards Kate, who turned AJ around to face his nephew.

"Alexander James Castle meet your nephew, Harrison Edgar Williams," Kate cooed softly towards the little guy in her arms, sporting breathing taking blue eyes, just like his father. Kate's eyes moved from her son to her grandson, and she gasped in awe. "Wow… he looks so much like you, Harry."

"I don't know," their son-in-law said. "I think he looks like Alexis. He's got her nose and hair."

"Well, I think they're both gorgeous," Castle chimed in, admiring his son and grandson. Wow… he was a father and a grandfather at the same time. Now he knew how Steve Martin felt in Father of the Bride: Part 2. His eyes flicked up to Kate's and he smirked. "Must be in the genes."

Kate rolled her eyes at him, yet conceded with a nod. "Must."

The End