If your sister got pregnant with your husband's baby by cheating...

If your sister got pregnant with your husband's baby, and decided to keep the baby...how would you treat the baby? It would still be considered your nephew or niece and the baby didn't ask to be born by cheating. So how would you react? Would you treat your nephew/niece harshly even if it's not their fault? Would you cut off all ties with your sister, the baby, and most likely ex husband? Would you treat the child like any other nephew or nieces?