Her mom is very controlling, and in the end, it REALLY hurts the kids.
Her brother might grow up thinking that women are slaves (Considering
he is the only boy in the house, and the women have to do his
bidding), or he could grow up to be even more lazy, etc. He tried to
get me a drink pouch in the fridge once, and accidentally knocked over
a glass of milk. Then him and my girl tried to clean it and got
yelled at for not doing it the right way. While she is certainly
entitled to raise her kids as she pleases, the little brother will be
lucky if he learns anything on his own. He is yelled at for doing
something himself, and his sister is yelled at for not doing it for
him.
Basically, back off of your kids. They WILL get hurt, they WILL get
sad, but dammit, they'll thank you a shitload when they're older.