If you see something, say something. Parents like that never change. Speaking with them will only cause ire between you and them. Instead, the only rational course of action would be to contact someone in a place of authority that could ensure those children have their best chances in life, and living with that woman who claims to call herself their mother is not best for them.
"Never trust a fox. Looks like a dog, behaves like a cat."
~ Erin Hunter
~ Erin Hunter