According to a WWI draft card, William Thomas MARS resided in Paxton, Keith County, NE in 1918. His birth date was June 6, 188[4?], and his wife's name was Lilah Maud Mars.
Do you have additional information, such as when and where Lilah or any of the children died? Do you know where Lilah is buried? If so, have you checked with that cemetery to find out whether William is buried next to her?