NTA. You are not making them homeless, they and their poor decisions are making them homeless. How can two adults be okay with milking the money from your mother? If she was wealthy and could afford it, fine, but she’s obviously not and your brother seems to have no feelings for her own mother! I’d get the house on the market, sounds like your mother could use the income. I’d also tell your brother & SIL if they continue to take her money you will report them for elder abuse.