In episode seven, Shore Leave, while testing the the taste of the sand outside with Marjory Stewart-Baxter, Salad Fingers and Marjory come across Hubert Cumberdale, next to a giant hole which Hubert supposedly dug himself. Inside they find a decomposing corpse.
Salad Fingers claims that it is his little brother, "back from the Great War on shore leave" and invites him in for dinner. Salad Fingers gives the corpse a bath, dresses him in a nice suit, and sets a table up for the two of them, serving sand as the main course. Kenneth collapses onto his plate immediately, and Salad Fingers offers to prop him up with a wooden dent-rail if he's "feeling rather slumberous."
After dinner and some light conversation, Salad Fingers cries when his brother has to "leave." Salad Fingers salutes, kicks Kenneth back into the hole, during which he's singing "We'll meet again".
It is assumed that this is the real younger brother of Salad Fingers. It is hinted that his brother was in the Great War, he may have died and was buried there; due to his insanity, Salad Fingers blocked out his brother's death and true whereabouts and switched them with the false idea that he was still alive fighting in the war. It is more likely that the corpse belongs to a completely unknown individual, with no explained background.