Hank is the "adopted brother" of Ron Wethers, orphaned at the age of 5, he was kidnapped and taken to be trained as an assassin,
Ron was one of Hank's hits, but something struck him as odd about the hit, he ended up trying to get close to Ron by applying to be his partner as Ron's assistant at his Private Investigation firm.
Hank decided that he would instead of kill Ron, would aid him in his work, and completely severed all ties to the
assassins who trained him, though they still want revenge on Hank, they're not going to lose any important assassins to take care of him.