how do i update/download an app if its forcing me to sign in with a different account??

hey so theres been a problem with my app store, my brother had to sign me out for a bit to get a phone number for my phone but now when i use the app store for anything like an update it forces me into signing into my old icloud account. i already tried making a new account and signing out and signing back in but it didnt budge. it keeps saying i have to sign into the old account, which i literally cant because the 2fa uses my brothers old phone number that none of us can access. its legit starting to annoy me now and i cant find a way around this until i wait 5 days for apple to do something. is there any way at all behind this???