I believe the Benjamin that is being discussed is the brother to William. William had a son named Benjamin but he also seemed to have a brother. This is evident by them both of them being listed on the 1767 Dobbs Militia roster (http://freepages.genealogy.rootsweb.ancestry.com/~paday/dobbers/military/malita.htm). This Benjamin was also on the 1769 & 1779 Dobbs tax list. The Benjamin listed as William's son was born in 1795.