We have the same mystery. Some tidbits of information FYI. A number of us believe Silvanus Allen bought land in Essex county in 1745. We think he had a Jeremiah Allen and Betty that sold it later. We think he was our Silvanus's Father.
We believe Silvanus was also the Father of Katherine Allen that married Lunsford Gouldman. She had 4 grand daughters named Julia, Margaret, Muriel, and Elizabeth Gouldman that she mentions in 1843 Spotsylvania will.
Family lore claims we were closely related to Ethan Allen, although no link has been found. We think it must have come through Molly. FYI