Coomer, William by wife Joanna had ... William ... William, Duxbury, m. Mabel Kempton, 1753 and had William. William, son, m. Priscilla Anderson, 1780.
↑ Estimate birth date of bef. 1732 is based on the assumption he was of legal age when he married in 1753. Depending on the exact year of birth, it may have occurred in Plympton (about 1730) or Kingston (if in born in the 1720's). Plympton looks likely because Source:Plympton, Plymouth, Massachusetts, United States. Vital Records of Plympton, Massachusetts, to the Year 1850, p. 76, contains the following entry in the Births section, that appears added by the compiler? Coomer, (William, it is said moved from Plympton to Duxbury, s. William and Joanna, [born] ---), but it does not help deduce his birth date.