His mountain clan, and family were a simple group living beneath the mountains until the red dragon came. It scoured the tunnels devouring and burning everything in its path. Brock, burnt by dragon fire, scarred, and grief-stricken from losing his wife and kids, was left to die in the woods.
His mind gone, he lived for years as a savage. Wandering about, occasionally helping the destitute and desperate who had no one else to turn to, he barely remembers much of the fatal event. But he hates dragons. He lives to slay every dragon he can get his hands on. His personal mission is to rid the world of their cursed kind.
His trauma has suppressed a lot of the sad memories, but he remembers he had a wife and children, and that a dragon slew them.