Guardianship of my nephew

My nephews mom just told me she violated her probation, convicted of welfare fraud. She's on probation for 4 years and her husband is going to rehab for heroin. She told me if she goes to jail she wants me to take my nephew. My brother is (his father) is also in prison for drugs. Which is no big deal, I've wanted my nephew out of that crazy mess for years. The problem is her other 2 kids. I don't want them to be sperated but I can't take on all three of them. I only have a 2 bedroom house and I have my own son. The only other family member willing to take them is 4 states away. I'm so stressed on trying to find out how this is all going to work. I don't want my nephews stepdad taking them he has his own problems to work out. I hate that my nephews parents couldn't pull it together for their kids sake. I'm so worried on how this is going to affect them all