His California death record indicates 1885 as his birth year but his WW1 and WW2 draft registrations both indicate 1881. Most other records are more in tune with that date of 1881, including his first Kansas state census record in Lincoln County in 1885 that shows him being 4 years old. As for the 1885 date, the informant was probably his wife, Esther "Essa" Devall Dohm Bernhardt and she may not have known the correct year.
Dennis A Bernhardt and Essa Devall Dohm can be found in the California Voter Registration database living at the same address from 1944 to 1956, the year before his death. (1948 is the only exception.) Both are found in the 1950 Census living at 12866 Admiral avenue in Los Angeles. No marriage record found as of this writing. Essa uses the surname of Dohm until the 1960 voter registration when she appears as both Essa Dohm and Esther Bernhardt, both names residing at 12866 Admiral av.
Dennis Bernhardt's first known wife was Emma Clarinda "Clara" Mack. According to the Springfield Leader and Press (Springfield, Missouri), Thursday, November 24, 1927, Page 8, Dennis and Clara were issued a marriage license in Springfield, Missouri under her then name of "Clara Heenan." Clara died in 1934 in Sioux City, Iowa. Her obituary with Dennis A. Bernhardt listed as husband can be found in Sioux City Journal (Sioux City, Iowa), Thursday, March 22, 1934, Page 10. He was her fourth known husband. Her headstone has her maiden surname only. Note that her Iowa death record indicates her death as being in 1935 but her obituary and headstone both indicate 1934.