It is not fraudulent as long as it is used within your blood relatives. Don't think using your father's PP for son is fraud. There are people selling QRs - that is fraudulent. The entire concept of add on cards is based on this - supposed to be given for blood relatives
Name mismatch PP is always rejected. That is known. You cannot explicitly use your named PP for some other person. However with surname matching it is possible. You just have to tell at the counter that the PP belongs to your son/daughter with surname