Martin Hermag Slikk ( born February 9, 1954, aged 64), is Leopold's grandfather and was Harold's father from 1975 to 1991 when he was a kid. His first appearance is when Martin tells Harold his troublesome, childhood when the brothers visited the village. Martin is married to Maria Slikk in 1974, in the AGK world, as Martin tells Leopold. Martin is the 55th oldest of the Slikk Family tree. Leopold is the secondary grandkid of Martin. In 1991, Harold traveled to Germany, in AGK logic. Joel Slikk is one of Martin's side-nephew. He is seen playing with Felix Slikk, Leopold's baby brother.
Maria Slikk (born July 17, 1957, aged, 65) is Leopold's grandmother and Harold's mother. She is seen in the bedroom watching tv.