Mary Welch Miles was concieved during her mother's marriage to John Welch. John Welch died on 25 May 1732 and her mother married Joseph Miles shortly after this on 25 Sep 1732. So Mary Welch Miles was born shortly after her mother's marriage to Joseph Miles.
Her stepfather, Joseph Miles, purchased of Edward Cogswell ninety acres of land, with a house, saw and grist mill, parts of lots 33, 34, 35, lying on both sides of the East Aspetuck River, New Milford, Conn.