Disclaimer: Still not the owner of Criminal Minds.
"Sweet dreams, baby girl." He kissed her cheek chastely, then turned ever so slightly away from her. He couldn't bring himself to go far from her, but he was trying to keep up appearances, albeit very shoddily. He liked sleeping next to her. He needed the comfort, too. It had been such a shitty case. But shitty case or not, he was struggling to pretend like he didn't want to fall asleep by her side, and wake up next to her each and every morning that he could. She had mumbled something in return that might have been 'you too', but also could have been 'let's get a zoo'. They were both way over their respective limits.
Derek was halfway to sleep when Penelope burst out laughing madly, rolling into him and shaking with fits of laughter.
"Breathe," he told her, laughing too. Her laugh was infectious. "What's so funny?"
"Incest," Penelope said, through gasps of laughter.
"Incest?" He raised an eyebrow. "What the…"
"Our little family, at the BAU. Hotch is mom, Gideon was dad. Rossi's our perverted step-dad, who occasionally flirts with the kids and mom makes him sleep on the sofa." They both laughed, recalling the stern talking-to Hotch had given Rossi for flirting with JJ. "Then Jayje and Em are my sisters, Elle the very long-lost cousin, and Reid is my kid brother. But you…you're like, a hot cousin twice removed or something. I don't know. We're family, but not in that way, yaknow?" Derek grinned.
"Yeah, you're my hot twice removed cousin too. Definitely don't see you as a sister."
"Right!" Penelope grinned. "You're my best friend, and you're family, but it wouldn't be weird if we kissed or anything."
"Exactly," Derek replied, moving ever so slightly closer to her. "It wouldn't be weird or incestuous if we kissed."
"No, not weird at al—" their lips met suddenly, though neither was sure who had started it. Penelope sighed into the kiss, every fibre of her body screaming one word repeatedly: finally. Derek used her sigh to part her lips gently with his tongue, deepening the kiss slowly, sweetly. Her arms slowly wound their way around his neck, bringing him just a bit closer. He took the hint and moved a lot closer, one hand grasping onto her lower back, the other going to her hair and stroking it, lovingly.
They broke apart to breath, and both smiled content. "Now that was a good night kiss." Penelope said, her breathing slightly shaky. Best kiss of her life? Probably.
"I'll say," Derek sing-sang. He looked so genuinely happy, relaxed and comfortable that she had to reach out and kiss him again.
And again.
And again.