Can my childsister father take my child if he never had her and pays child support

Is paternity established? If you were not married, this person would have no legal rights towards your child whatsoever. If paternity is established,  he would have the right to request placement of the child, but to win a custody battle against you, he would basically have to prove you are an "unfit mother." That would require that he prove in court that you are either an alcoholic, drug addict, or  have serious criminal problems, mental health issues or child abuse issues against you. The law in Wisconsin does not favor giving one parent primary placement and making the other parent a distant visiting parent; rather, the law for nearly the last 16 years favors the courts giving both parents, substantial and meaningful periods of placement which most people consider shared or equal placement. Without knowing the age of your child or any other facts, it is difficult to answer your question in terms of what his actual chances might be.