How should I go about bringing up this issue to my family?

a while after my moms mom died, my grandpa had a girlfriend, and they had a child. making him my uncle. while my grandpa never married her, my uncle has become part of my family, and more of my brother. my parents and I never liked my grandpas girlfriend, because she has bad habits and is, in my eyes, a terrible influence on my uncles life.

so to the problem, we got my uncle an iPod touch for Christmas, and he loved it. but his mother keeps taking it, and using it. He has just gotten it back from her yesterday after two weeks. While he was at our house yesterday, i was playing a game with him on it, and there were emails notifications. my uncle doesn’t email, so i looked, and they were from a dating site. one of those “sugar daddy” things.

i turned the notifications off, so my uncle wouldn’t find this out, he is eight years old, and now can read. i confided in my boyfriend about the problem, and he said to look the profile up, to see if there was an actual problem, because she still claims to be “with” my grandpa.

there were some lies on the profile, but the worst was she described her children, even my uncle which really bothered me. and she also said “relocation is an option”. i haven’t told my parents about this yet, because i don’t know how to go about telling them and bringing this up as a family issue, if she has intentions of leaving and uprooting my uncle.

and for people who don’t think this is me or my families business, it is, my uncle is 100% part of my family, even to the people on my dads side. any help would be greatly appreciated. thanks so much.