ooh~ i love that! i could definitely get behind the ol' enemies to frenemies trope (would rather that than them turning into mortal enemies, if that's okay.) maybe they could have been something along the lines of like childhood rivalries? and were often just egged on by the animosity that was also between their parents?
do you a preference to gender? i'm very much starting from scratch and just trying to fill lines to see if i can get something formative in my head so i'm super open to suggestions for pbs and what not too.