everyone's an angel non-cannon au, abo dynamics??, omega!dean, alpha!castiel

[cptnspacecase]

I don't remember the title or anything, but I do remember what happened. The setting was an AU where some magical world was entirely populated by angels (I don't even think humans were a thing), and Sam and Dean were run-of-the-mill common angels. Sam was an alpha, and Dean an independent omega who didn't need no alpha and was scorned because he was so "old" and undesirable as a mate. There's this ball/party thing that happens every year where everyone rubs elbows and also looks for mates, and I THINK Sam and Dean went because Dean wanted Sam to have the opportunity and not end up like him, even though Dean always ended up the butt of a joke at those things. But that bit's kind of fuzzy for me.

Cas and Gabriel are powerful archangels and basically considered nobility/royalty, with Cas being an alpha and Gabe an omega. They're at this shindig, and Dean spots Cas and is like, holy shit I actually want this guy?? Only their society is super formal about roles and introductions and shit, so when he tries to go up to Cas -- who's very traditional when it comes to customs -- without a family member to introduce him, Cas ignores him and walks away, leaving Dean publicly humiliated. But they work it out eventually.

Dean/Cas are the primary pairing, but I'm pretty sure there was some afterthought Sam/Gabe.

Thanks to anyone who can help! I've spent hours trying to find it, and it's bugging the hell out of me.