AUTHOR'S NOTE: Yet another fill I started anonymously and am claiming now (and actually, I posted this on my AO3 weeks ago and am just now putting it here). It just got so long and each part is so long that LJ's 4300 character limit in comments became super frustrating. Plus, I came up with an awesome collage for a banner. And the prompter loved what I had so far so I didn't feel as anxious.

Yes, I wrote Destiel. Yes, I usually say I only write Sastiel or J2 or Cas & Dean friendship. I saw this prompt and couldn't resist the eggpreg part and I read enough Destiel because it's 90+% of the fandom and I love reading so I'm not gonna turn away a good plot, and I kinda grew a soft spot for it... And I did like Dean beforehand anyway, so... Sue me. I'm branching out a bit. Cowers in the corner

"Cas," Dean moaned, arching his back and shoving his ass back onto the angel's cock. "Gonna come…"

"Not yet," Cas panted, gripping Dean's hips tighter and holding the hunter in place. "Need… to lay first."

Dean groaned in frustration and dropped onto his forearms, keeping his ass up for Castiel to pound into. "Then do it," he snarled without any real heat, followed by a whimper of pleasure as his cock twitched with impending orgasm. He gripped the base in a fist tightly to hold off.

It only took Castiel a few more thrusts before he came into Dean's ass, groaning deeply as his cock pulsed. Except the angel didn't release just semen like a human male. Amid the wash of fluids filling Dean's ass were eggs – eggs containing the angel's true celestial DNA. They were about the size of a marble as they slipped from his cock into Dean's ass, making both men grunt and groan at the bumpy sensation.

"Now?" Dean panted, desperate for release.

Castiel pulled out once he'd deposited his load and draped himself over Dean's back. One hand braced the hunter's abdomen while the other cupped at the end of Dean's cock. "Now," he commanded.

Dean whimpered as he furiously stroked himself, chasing desperately the release he'd been denied. When he finally came, Cas's name on his lips, the angel collected as much of the hunter's release as he could. When Dean finally stopped spurting, Castiel sat up and used his free hand to scoop up Dean's come in dollops, carefully working it into the hunter's ass until all of it was gone.

"We do it?" Dean asked, keeping his ass upright until Castiel gave him the okay to lie down.

"We did," Castiel confirmed. "With my grace encased in the eggs and your semen providing the other parental DNA, we shall have children, Dean," he said, a wistful note lacing his voice at the end.

Dean hummed his agreement, unable to stop a small smile of his own. "How many do you think you put in there? I was too busy needing to come to pay attention."
"Three or four," Castiel said. "At least."

"Holy shit!" Dean exclaimed, pushing up onto all fours and attempting to get up before Castiel gently pushed him back down with a reminder that they needed his ass up to let the eggs catch. "Four?! I can't push out four kids, Cas!"

"You won't be giving birth to actual children, Dean," Castiel explained. "You will incubate our eggs for several months and then, when they are fully matured, you will lay the eggs."

"Still, that's four kids-"

"Fledglings."

"-for us to raise, Cas!" Dean stressed, ignoring the angel's correction."I know I said I'd like a big family but I didn't mean all at once."

"Do you regret this decision?" Castiel asked even though it was far too late to back out now.
Dean was silent for several seconds then shook his head, reaching back with one hand to clasp at one of Castiel's. "No, Cas, I don't. I want kids with you, a family, no matter how many we have."

Castiel smiled affectionately and ran his hand down the length of Dean's spine, watching his mate's relaxed features until he deemed enough time had passed for the eggs to catch.

They would know in time if Dean caught and was now pregnant.