Several possible areas to look in. A will if it exists is often the best confirmation. For example if Mary Hadfield's father's will exists it may mention grandchildren or her siblings might have left something to nephews. Look and see who were the witnesses at Henry and Willliam's marriages there may be clues there. Check the censuses for possible relatives living with people of interest(warning:the relationship is not always given explicitly and nephews, nieces sometimes appear as servants).

With luck something may turn up. Good hunting !