The Twins' Great-Grandfather

Ruffnut and Tuffnut's Great-Grandfather is mentioned only once in the Dragons: Riders of Berk episode, "Dragon Flower." His name is unknown. It is also unknown which side of Ruffnut and Tuffnut's family he is from, their mother's side or their father's side.

Biography
At some point before the events of "Dragon Flower", Ruffnut and Tuffnut's Great-Grandfather died and had his skull and clavicle preserved. The Twins later gave the skull to Trader Johann in exchange for a Target Statue.