When James Potter is hit with a spell which makes him lose his memory, everyone is understandably freaked out. Everyone except for James, of course, who is too busy trying to reassure his boyfriend that he hasn’t forgotten him and never will.
Except, James Potter is single, and Regulus Black has no idea why he seems to think otherwise.
https://archiveofourown.org/works/55254271
Or, the one in which James Potter wants to prove he'd be a good boyfriend to Lily Evans and comes up with the brilliant plan to fake date Regulus Black his way into falling in love. It doesn't quite go as anyone expects.
https://archiveofourown.org/works/38344720?view_full_work=true
Or, Regulus mistakenly sends James a letter he wrote confessing his undying, completely mortifying, and extremely impractical feelings for the boy, and now he doesn't quite know how to proceed living his life after this embarrasment. But James might have an idea.
https://archiveofourown.org/works/50868529
Sirius and Regulus run away and end up staying with the Potters. James would very much like to fix their trauma, except he can't; but when Regulus tells him that he left his teddy bear at home, James decides that the best course of action is to break into the house and get it back for him.
https://archiveofourown.org/works/48394999?view_full_work=true
or, james potter sees regulus capture the snitch in record time and absolutely goes insane for the man!
https://archiveofourown.org/works/52474543?view_full_work=true
in a parallel universe Sirius grabs Regulus' arm right before he vanishes into thin air when he's sixteen
https://archiveofourown.org/works/23829958/chapters/57262012