So annoyed as I usually have a good memory for fics but I am totally blanking on this one.
It's an AU, I believe Arthur is a bartender or works at a restaurant. Mal is his best friend and is going out with Dom. Arthur starts going out with Charles who is very posh and disliked by Mal due to a feud going way back due to their families being friends, but she gets on much better with Charles's twin brother Eames, who runs an antique shop?
It's Arthur's birthday, Mal organises drinks but Charles takes Arthur to an exhibition or something, drops Arthur off at the bar where it's packed and he's squashed next to Eames, they all play drinking games and get drunk. Arthur has to fetch his wallet from Eames the next day and Eames has bought a breakfast burrito with chorizo on it?
There was a country estate involved, and Mal sitting on Dom's knee, and all the rest is lost to me as I never finished it or bookmarked it, boo. Maybe it was a work in progress, but it was definitely a long fic!
How can I remember all these details but not the author or the fic itself? HELP ME INCEPTFICFINDER, YOU ARE MY ONLY HOPE!
[EDIT] - Thank you so much for helping me find this, it is indeed
Brotherly Loathing by anon, currently a wip! Bartender bit was wrong, but I know there are several I'd read with that gorgeous scenario!