"Massachusetts Births and Christenings, 1639-1915," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:FZ95-HJX : 10 February 2018), Sarah in entry for Francis Josselyn, 27 May 1757; citing HANOVER,PLYMOUTH,MASSACHUSETTS, ; FHL microfilm 0874289 IT 2.
"Massachusetts Marriages, 1841-1915," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:Q28L-M1V3 : 28 November 2018), Francis Joselyn and Mary Hill, 17 Feb 1782; citing Pembroke, Plymouth, Massachusetts, United States, State Archives, Boston; FHL microfilm 906,748.
It may be possible to confirm family relationships with Francis by comparing test results with other carriers of his ancestors' Y-chromosome or mitochondrial DNA.
However, there are no known yDNA or mtDNA test-takers in his direct paternal or maternal line.
It is likely that these autosomal DNA test-takers will share DNA with Francis: