App store asking for password of different Apple ID?

I have an iPad pro that once belonged to my mother, which then got passed to my brother before he finally gave it to me. While they each used it, they had it registered to their Apple ID. I have been using it under my Apple ID for some time now without issue, with it occasionally asking for my mother’s ID password with an option to edit my settings, which I always just hit “cancel” on because I didn’t know what it wanted me to do. I just tried to update my apps and had a difficult time because even though I was signed into my Apple ID on the app store, it kept saying my password was incorrect and I eventually realized the only one that worked was my brother’s password. How can I get the iPad and app store to stop splitting up the Apple IDs in this way? It’s extremely confusing and I can’t figure out a way to remove their information from the settings or App Store.

EDIT: I’m wondering if the reason it wanted my brothers password was because most of the apps were downloaded with his Apple ID. Does that have anything to do with it?