I need some advice. My 3 yr old and 7 yr old nephews are being "unschooled" by my sister and I don't think it's good for them

My sister, whom I love very much, has two boys, 3 and 7. She unschools them, which means they don't go to school, and they don't have any kind of structured curriculum at home. She started this a couple of years ago and then was told by her marriage counselor that that wasn't a proper option and that if the older one wasn't enrolled in school then she'd get cps involved. So she enrolled him in school. Since then, my sister has gotten divorced and then involved in a polyamorous relationship. So now her and my nephews live with her boyfriend and his other girlfriend and her young daughter. She says they're all being homeschooled by his other gf. I keep their boys one or two days a week and she keeps my 5 mo old a couple days a week so I see a lot of them. From what I can tell none of the kids have any kind of structured curriculum. There's no evidence that any of them are learning anything. It's especially important for the 7 yr old. He's very bright and creative and loves to learn but all he does is play video games and watch youtube. If I say something to my sister she'll just shoot off a bunch of stuff she read about it, she's so stubborn. She will just act like I don't know what I'm talking about. And ultimately it's her children. What should I do? via /r/Parenting http://ift.tt/2zeI7Ea