i don't know how close you were with your sister but I think you should be sensitive that she is in a very difficult situation that's why they transferred back to your house. It's not easy raising kids and having debts or money problems. "Not minding them" meaning wala ra kay tagad nila is like being suplada to them and they feel that they don't belong to "your" house. Once you'll give birth to your own kid you'll probably understand the situation.