How would you deal with this situation?

Your dad and stepmom, who have never been there for you and you are not particularly close to, call to say she has a horrid, debilitating disease. They want to sell their house, file as separated to get medicaid, build an in law suite onto your house and live there. They say all their debts won't effect you, and you won't have to every pay a thing for them. They have no savings, no income except social security and anything left from the house selling that didn't go to medical bills etc.. Sound good? Sound like it will go smoothly for you? Oh yeah, by the way your married with two kids, one on the way and two mortgages. What do you do?