You might try a marriage search for each of the children they listed for a lead. There were Lyons in NJ - my interest. Grove/Sylvester/Lyons inter-marriages from there. There is a submission for an Elizabeth Bockover in NJ. By the birth dates, Sylvester is 20 years older than Elizabeth. Sylvester was no doubt married before one or two times before his marriage to Elizabeth. In that time period they had large families. Perhaps his first marriage was to a sister of Elizabeth. A Richard Grove married a Hannah Lyons in NJ. Richard's brother Sanuel married an Elizabeth Sylvester in NJ. A namming pattern that I have run across is nameing the first daughter of the 2nd marriage after the first wife. Being helpful I hope.