Unless your sister is wiling to give you guardianship over your nephew, gaining custody would be difficult. If your sister is not taking care of her son, this may be a matter to be addressed by Child Protective Services. If CPS was to intervene, they could place your nephew with you and could, depending on the facts, move for termination of her parental rights. If her rights were terminated, you could then petition to adopt your nephew.
Answered on Jan 23rd, 2013 at 2:32 PM