He married Mary Geroe, 20 June/February 1857, reportedly in Newark, Essex County, New Jersey.
Jacob and Mary were in the 1860 census of Aurelius, Cayuga County, New York; he was 27 years old and a carpenter and joiner by occupation. Mary was 23, born in New Jersey. With them was a son, Herbert, five years old, apparently either their son born before their marriage, or Mary's son before she married Jacob. Mary died before the 1900 census was taken, as Jacob is listed as a widower and living with his son Ackerman and daughter Maizie.
Children of Jacob M. and Mary (Geroe) Oatman:
2008 Herbert, b. ca 1855, NY
2009 Ackerman Geroe, b. ca 1873, NJ. It is possible this is the A. G. Oatman listed in the 1880 census of Middletown, Rutland Co., VT; he is listed as 31, a farmer, b. in VT; his wife, Salonia?, age 27, b. VT, and apparently a hired hand named Edward Haley, age 35, b. Ireland. (Jacob and Mary reportedly not married until 1857.)
2010 Maggie, b. ca 1864, NY
2011 Emma, b. ca 1866, NY
2012 Maizie B., b. Feb 1879, NJ
LDS Archive record submitted by Josephine DeLand Strong
Patricia Ann Godsey, Springerville, AZ
International Genealogical Index
1860 census, Aurelius, Cayuga Co., NY
1880 , 1900 census, Paterson, Passaic Co., NJ