Dad comes from a very musical family, but never sang much. In WWI he was part of his "fleet orchestra," a bunch of guys with ukuleles and one clarinet -- they billed themselves as "Ike Eisely and the 99 Nasty Nose-Pickers, singing 'Oh, You Booger'"! Wonder what that was like? He never has given up the secret. Years later, after seeing "The Ballad of Cat Ballou," he would occasionally break into a growly rendition of the theme song's opening line.
My mother, on the other, hand, is mostly tone-deaf, but always sang around the house. She was pretty much famous for drifting from one song into another one with a similar musical phrase; one of the best of these unplanned medleys was probably "Goldfinger... wider than a mile..."