He married Ora Anna Wilkins (1859-1879) on 28 Feb 1878 in Clay City, Clay Co, IL, and is the father of Charles C. Clem who was born in Dec 1878 and living with the family in 1880. Perhaps she died in childbirth.
He was married a second time to Prisilla Willard on Jan 22 1884 in Macon Co, IL.
He was married a third time to Mary A. Herrod on Jan 5 1898 in Macon Co, IL.
Married and living with his wife Mary (36, Canada) of 2 years in the 1900 census for Harristown, Macon Co, IL; working as a farm laborer. Living with them are children from his second marriage: Elmer J Clem (Apr 1886, NE), Ethel May Clem (Aug 1888, NE), Carl Clem (Aug 1895, IL), and Orvil Clem (Jan 1898, IL). Based on the listings of their parents birthplaces, it appears they are all her children from a prior marriage.
They are still listed in Decatur in 1910, which states that it is his third marriage, that they have been married 13 years, and he is working as a laborer at odd jobs. They now have another son, George H., from the new marriage.
By 1920 they had moved to Oklahoma, where John is listed as a farmer (67, IN), with Mary (57, Can) and only the boys Carl, Orville and George living with them.
In 1930, John is still in Oklahoma listed only as J. T. Clem, age 78 and a widower. His “son” Orville is the only one listed with him.