HELP- probelm occurring for years!! Old password on new devices???

My mother, brother, and I all use the same i-tunes account on the same home computer. However, I deauthorized my first account and have a new one completely, but when my mom tries to update apps on her phone it asks for my old id's password? I'm not sure why its asking for my id in the first place on her iphone, nevertheless one that I don't use anymore. I have been trying to solve this for years and I would really appreciate some help here.