What would you do if this was you?

Your father and step mother (whom you've never been close to and have at times been estranged from) discover your step mother has a serious illness that will only get worse as time goes on. They have no money due to a mix of high living and very little saving and now they come up with this idea, they will sell their house, build an in law apartment to yours and move in. They will be legall sep. so medical bills will be covered apparently by medicaid. Oh yeah and they have a dog that she loves more than her grandkids (and you have a wife, two kids and one on the way with two dogs of your own)....tell me your decisions. THX