Agira Ryūdōin

is the father of Jakō, Rokkaku and Genshō.

Background
Some time in the past he fought Might Guy and was defeated. In the fight he was badly injured and died soon after. His sons tried to take revenge on Might Guy, but in the process they realised that they misunderstood their father.

Trivia

 * Interestingly, he has a tattoo-like arrangement of tomoe on his forehead, somewhat resembling the Cursed Seal of Heaven.