The straight guy that texts Derek every once in a while for a drunken hookup is getting married and wants another go at Derek’s tight ass. Derek comes as requested and the two hook up in the back of the very church the groom is about to get married in in a matter of minutes. The guests are already in their seats, the bride is in her dress, and the groom is balls deep in the guy he’s been fucking on the side.
Derek is dating either your character’s older brother or dad and is something of a kept boy. Your character knows what’s Derek is there for and has heard how well Derek can take a dick. So, when the brother/dad is distracted during a party, your character finds Derek alone upstairs and decides to see how good his ass is for yourself, potentially leading to the two of them continuing to hook up behind the brother/dad’s back.