"Wisconsin, County Marriages, 1836-1911," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:XR24-TPB : 3 June 2016), Willoughby C. Mendenhall and Mary Missenskie, 28 Dec 1873; citing Menasha, Winnebago, Wisconsin, United States, Wisconsin Historical Society, Madison; FHL microfilm 1,275,611.
Year: 1850; Census Place: Clinton, Rock, Wisconsin; Roll: M432_1005; Page: 449A; Image: 475.
Year: 1860; Census Place: Clinton, Rock, Wisconsin; Roll: M653_1430; Page: 221; Family History Library Film: 805430.
Year: 1870; Census Place: Janesville Ward 1, Rock, Wisconsin; Roll: M593_1736; Page: 196A; Image: 74721; Family History Library Film: 553235.
It may be possible to confirm family relationships with Willoughby 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 Willoughby: