In most written records his name was given as William Paul (e.g., their son Jesse's obituary identifies him as son of "the late William Paul Dehart and Susan Jones" – see Jesse's notes, and his tombstone is labelled "W. P. Dehart" – see Susie's notes.) But all his children are consistent in naming their father as "Bill John" Dehart, and a few records do list him as W. J. Dehart (e.g., his daughter Laura's marriage record.) According to William Voigt, the reason he was called “Bill John” was because his father was named John.2

Ora Dehart (youngest son of W. P. and Susie), interviewed by Phil McBrayer in 1993, said that his father Bill John Dehart had siblings named Al, Jimmy, Kern, Sarah who never married, and another daughter who married a Caudill. Ora did not remember his grandparents' given names, but the list of children (except for Kern, which may be a nickname for Hazel Green) matches those of John Dehart & Nancy Bumgartner.

Ora also said that Bill John's first wife was Steve Conn's sister, and that their children (Ora's half-siblings) were Jack Dehart who married Martha Ann Clark, Jennie who married a Mynier, and Lucy who married a Warren. Ora lists his full siblings as Boone who married Annie Jent, Laura who married Jesse Crose, Lizzie who married Willy Crose, Frank who married Virgie Brown, Jess who married first Mandy Jane Mabry then Nellie Trent, Ollie who married Charlie Thornsbury, and Rosa who married Ramsey Wright.

Elliott Co. court records list marriage of Wm. Dehart and Elizabeth M. J. Dehart on 30 Dec 1875. (From published index; I haven't consulted the original to see if it has further details.) William and his bride were first cousins, their fathers being brothers. She was usually known as Mary Jane, using the Elizabeth only in official records (this seems to be a Dehart pattern.)

1880 census of Elliott Co., KY, Martinsburg precinct, enumerated 10 June, lists on p. 15 as family #111:
DeHart, Wm. P., 26, farmer, b. Ky Va Ky; Mary J., 24, wife, b. Ky Va Ky; Jackson, 3, son; b. Ky Ky Ky; Lucy B., 1, dau; b. Ky Ky Ky.