Maybe someone can look at the death records of Charles, Mary, Gertrude and George, and obits of Gertrude & George.
Social Security Death Index
Name: George E. Crober
Last Residence: 54956 Neenah, Winnebago, Wisconsin, United States of America
Born: 24 Nov 1905
Died: 20 Jun 1995
State (Year) SSN issued: Wisconsin (Before 1951)