I have a question about rotting teeth?

my good friend has some rotted teeth. she says it is a disease that runs in her family. her brother, mom, and dad have the same problem. she was also bulimic at one point in her life, so that might have made her teeth rot faster than her brothers. i know her parents are druggies, and she and her brother like to snort pain killers...but when we were in middle school together she did have bad teeth and that was b4 she got onto drugs...i just wanted know if sher teeth rotting can be hereditary and just got worse fast becaue of her belemia and drugs