There were some things about his relationship with Castiel that Dean seriously wished he'd known beforehand. Sure, he'd gone into the relationship knowing the angel was a quirky, meticulous, infuriating son of a bitch, but if he was being completely honest, that was part of the reason he'd been so attracted to Cas in the first place.
However, after the years they'd spent together, Dean slowly began to recognize that in addition to Castiel's seemingly endless quirks, there seemed to be some major cultural differences between them as well. It took awhile, but Dean liked to think he was moderately proficient in recognizing which traits were just Cas being his quirky self, and which ones were more culturally-centered.
Over-thinking pornos was definitely a Castiel-exclusive quirk. The other angels seemed to grasp the concept of porn quite easily. Hiding possums and raccoons in the bunker was another quirk Dean was still trying to deal with.
On the other hand, always standing ass-deep in people's personal bubbles seemed to be a culture thing. To Dean's never-ending annoyance, all the angels he'd met were some serious personal space invaders, and none of them seemed to find anything wrong with it. Especially the cherubs.
Another thing Dean had been fortunate enough to know beforehand was that Cas had a huge family. And it wasn't like the extended family you only had to suffer through on the holidays; these were all brothers and sisters. Thousands of them.
Not that they were on the best of terms most days—nine times out of ten, when another angel showed up, it wasn't to catch up over Sunday dinner. He'd honestly lost count of the number of times some feathered asshole had just appeared behind either himself, Cas or Sam, trying to stab or smite the shit out of whoever they could get their hands on. Knowing these jerkoffs were family didn't make much of a difference in Dean's eyes, but it at least allowed him to understand why Cas got so moody after fighting with them.
What he did not know, however, was that this psychotic angelic family was expanding. Dean was, admittedly, no expert on angels, even after the number of times he'd shared his bed with one. Neither was much for pillow-talk, and needless to say, the topic of basic angel anatomy hadn't come up in conversation yet.
Perhaps it should have.
Because the last thing Dean was ever expecting Cas to ask him was whether or not they should name their son "John".
"Our son?" he repeated flatly, and Cas tilted his head slightly as he replied.
"I'm fairly certain the child will be male." His words were slow and precise, and his eyes were fixed on Dean's face, searching for any inkling of a response.
"Where the hell are we gonna get a kid, Cas?" he asked, grinning in spite of himself. "No adoption agency in its right mind would give us custody of anything, and it's not like we can just swipe one off a playground." Dean didn't miss the uncomfortable scuff of the toe of Cas' shoe against the pavement, and his stomach dropped faster than the angel's gaze. "Cas, you didn't."
Cas looked up quickly at Dean's panicked tone. "I did not steal a child, if that's what you're insinuating."
"Okay, good to know we're not creepy child abductors," Dean said with a frown. "What's with the kid-talk, then?"
The angel's lips parted slightly, and his eyes narrowed. For a moment, he looked as though he was about to say something, but changed his mind halfway through and just shook his head instead.
"Will you just spit it out already?"
"Why do you assume I'm going to steal a child?" Cas asked bluntly, frown deepening into a glare.
"I didn't mean it like that," Dean said with a short laugh. "I just meant, where else would we get one?"
For a moment, Cas looked genuinely bewildered. "I assumed you of all people would understand the finer points of reproduction," he said. "Especially considering your insatiable sex drive."
Dean laughed, and Cas' face seemed to soften slightly. "Cas, buddy, I hate to burst your bubble, but I think you might've misunderstood a few things." When Cas didn't reply and instead looked even more confused, Dean elaborated, "We're both guys. And the only, uh, humans that can have babies are the ladies."
"I am not a human," Cas said, exasperated.
"Yeah, yeah, I know." Dean interrupted. "Believe me, I know. But you're in a dude's body, so the same rules kinda apply."
Cas seemed to be searching for words again. "I don't think you understand," he said pointedly. "I am not human. The laws of human biology don't apply to angels."
Dean's eyes widened almost comically as Cas' words finally began to sink in. "Cas, are you pregnant?" he asked, sounding slightly choked.
"In a sense, yes, but not the—" he trailed off hesitantly, not seeing any point in finishing a sentence Dean was very clearly not listening to. "Dean, are you alright?" Dean was very obviously not alright. He kept mouthing words like 'what' and 'how', and seemed deaf to anything else. "Dean!"
Dean looked up sharply, still looking utterly bewildered. "Sorry," he muttered. "It's just, you know, not every day you find out you got another dude pregnant."
Cas' eye twitched. "I am an angel of the Lord," he snapped irritably. "Not 'another dude'."
"Right," Dean said, rolling his eyes. "Because that makes it so much easier to wrap my head around. Cas, this is a kid we're talking about! Our kid!"
"I'm aware of that!" Cas exclaimed finally. "That's why I'm asking you what to name it."
"Oh." After a few steadying breaths, Dean finally seemed to calm down. He chewed his tongue in thought for a second, then said, "Uh, let's definitely not call him John." There was a brief silence as Cas stared his usual soul-searching stare, and after a moment, Dean hesitantly reached out to rest his hand on Cas' stomach.
"What are you doing?"
"Trying to feel the baby," Dean said with the slightest hint of a smile slowly creeping its way onto his face. "You still look the same. How far are you?"
"Dean, my vessel is not pregnant," Cas replied. "I am. Your human biology wouldn't allow it."
Dean clapped a hand over Cas' mouth, and the angel's eyes widened indignantly. "Cas, you're ruining the moment," he said with a laugh, wrapping his other arm around Cas' waist and pulling him into a quick hug. "C'mon, Sammy's gonna flip his shit when we tell him!"