Bill's grandfather is a character that appears in the pokecalypse series. He is a retired scientist and researcher who passed his legacy onto his son and grandson. He has two living relatives, after his grandson Bill died due to an attack by cursed pokemon. An unnamed son, presumably travelling the pokemon world fighting the plague, and an unnamed granddaughter living in goldenrod city in Johto

Grandpa Bill is saved by Misty, Vergil and Cole. After mourning his grandson, he instantly takes aliking to both Cole and Vergil, and starts seeing them as family, seeing that the boys have no family left, just like him. The fact that Cole takes a liking to science adds more to this fact, to the point where the boys start calling him grandpa at some point