Frank was born in Paisley, Scotland, the youngest of three children of Margaret and Richard Castle, a bookmaker. Of Irish descent, he was brought up in a strict Roman Catholic family. Frank spent the first few years of his life in Montreal, Quebec, before the family returned to live in Scotland.
Frank traveled to US to study with his uncles deciding it would be better and for him and besides he would get to be in a new place were not everything is green, monotonous and boring. He was an average student academically, but excelled in athletic pursuits. He started kick boxing when he was 12 and got a liking for it. Even though he never got to a level to compete as an amateur fighter, he was good enough to spar with them.
When he turned 18, he turned his knowledge of kick boxing and his easy going personality into a work as a bouncer in the City. No one expected him to last long, but he loved his job and stayed at it, until he got injured in a bar fight. He got a month of rest and too much time to waste, besides going to college was not his greatest thing to do he was just an average student at it. When he turned 19 he decided to leave college and just sign up for the Army. The soldier life was boring and filled with endless drills, making Frank regret his decision and hoping to find something else to do or travel now that he was on leave and just working in the army base in the warehouse working the supplies.
