"Vermont Vital Records, 1760-1954," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:XFVL-M8L : 17 October 2017), Josiah Josselyn in entry for Ruth Howland Josselyn, 16 Aug 1848, Death; State Capitol Building, Montpelier; FHL microfilm 27,600.
"United States Census, 1850," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MD9K-KV5 : 12 April 2016), Josiah Josselyn in household of Lewis Josselyn, Lynn, Essex, Massachusetts, United States; citing family 2060, NARA microfilm publication M432 (Washington, D.C.: National Archives and Records Administration, n.d.).
It may be possible to confirm family relationships with Josiah by comparing test results with other carriers of his Y-chromosome or his mother's 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 Josiah: