Brother cat attacking each other?!

Hello all, so I have around 6 year old orange domestic shorthair i think (just picture ur avg house cat!) and they’re twin brothers. they have always play fighted since we got them when they were mere months and suddenly things have started to change. suddenly, cats are fighting more aggresively, fur is getting thrown around, it actually sounds painful now, and some hisses. it never lasts long and they’re not constantly arguing and can tolerate each other afterward but today it was even worse. i was giving cat 2 lets say more attention than cat 1 who is a MASSIVE attention seeker and cat 2 was calmly meowing at me just to get some pets while i was in the living room, smth he rarely does. suddenly, cat 2 comes out of nowehrre and starts sniffing his ass and then starts meowing loudly and actuakly attacking him as if trying to deter him away? i broke them up and a few minutes later i brought cat 2 closer to cat 1 and cat 1 meowed strangely before cat 2 ran off somewhere. is this normal?! im scared these two brothers suddenly hate each other i want them to be friends. Also, FWIW cat 2 caught a chipmunk the other day something neither have ever done (they are indoor cats, only go outside to our backyard ever so often bc we have a lot of fleas in this area) and both of them seem totally riled up since. not sure if it has anything to do with it. Please help!