Claiming Adult Dependent

Can someone claim an adult dependent, who is a qualifying relative, on their taxes if the person claiming them has little to no income but receives SSI and uses that to provide support and pay bills? 

 

My sister wants to know if she can claim our uncle on her taxes. He lives with her and does not work. She gets SSI and also doesn't work but provides support for both him and her. 

 

Turbotax program says she would qualify for the stimulus money for claiming him as her dependent.  However the support she provided is not earned but through SSI.  Even with no income it shows that she still qualfies for the extra stimulus money for him. But he already received his stimulus last year. Will she have to pay it back if she files and claims him as her depedent? Should she not claim him to avoid double dipping as some people call it? 

 

Thank You.