Frederick Nielsen was born 25 October 1875 in Lexington, Lee County, Texas, United States to Ole Nielsen (1829-1878) and Elizabeth Pedersen (1834-1889) and died 21 April 1969 Mesa, Maricopa County, Arizona, United States of unspecified causes. He married Mary Eliza Holgate (1882-1973) 19 December 1899 in St. Johns, Apache County, Arizona, United States.
Children
| Name | Birth | Death | Joined with |
| Nellie Magnolia Nielsen (1901-1985) | 1 June 1901 St. Johns, Apache County, Arizona | 14 June 1985 American Fork, Utah County, Utah | Hugh Richey (1896-1979) |
| Mary Eliza Nielsen (1903-1978) | 25 June 1903 St. Johns, Apache County, Arizona | 6 February 1978 Farmington, San Juan County, New Mexico | Moroni Forest Richey (1893-1932) |
| Elizabeth Augusta Nielsen (1905-1905) | |||
| Louie Louise Nielsen (1906-1995) | |||
| Frederick Moroni Nielsen (1908-1934) | |||
| William Ole Nielsen (1910-1993) | |||
| Edward Zenic Nielsen (1912-2003) | |||
| Olive Eve Nielsen (1914-2006) | |||
| Lenore Nielsen (1916-1998) | |||
| Eva Nielsen (1918-2000) | |||
| Nina Nielsen (1920-1920) | |||
| Roland Holgate Nielsen (1921-2004) | |||
Siblings
