Kinsella was born the son of cab driver George Kinsella and his wife Deborah, a school secretary. He has a half-brother, three half-sisters and a younger full sister. Like his older half-sister Brooke Kinsella, who played Kelly Taylor in the BBC soap opera EastEnders from 2001 to 2004, Kinsella had been involved in acting and he had a bit part as Tyrone Dooley in a 2004 episode of The Bill. He was a popular and academically gifted student. Friends spoke of his caring and comical nature, adding he was "full of energy" and that he was "the life and soul of his class".