First wife was Rebecca Bowditch of Rehoboth, Ma., who d. 23 May 1816.
Second wife was Abia Trask: "Massachusetts Marriages, 1695-1910," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:FHPG-YQY : 9 February 2018), William Southwick and Abia Trask, 01 Jan 1823; citing reference ; FHL microfilm 855,377.
Daughter: Anna Remington
Sources
↑ "Massachusetts, Town Clerk, Vital and Town Records, 1626-2001," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:Q29P-978D : 3 November 2017), William Southwick, 04 Jun 1786; citing Birth, Mendon, Worcester, Massachusetts, United States, , town clerk offices, Massachusetts; FHL microfilm 855,377.