You are not being selfish. I Had some similar issues with my husband trying to get his family to come stay with us too until they can get jobs.. Thank God I fought that decision and won!!! I too felt selfish. But at the end of the day it's your mental state, your money because basically you will be taking care of them until the sister gets a job that could take a while because she doesn't have a authorization to work anyways, right? , all your bills will go up..no privacy.and the mother won't have insurance so what's the point... sit down and talk to your wife about all your concerns.
Why do people even say the want to move here like its an easy process????