Sean Bennet is the half-brother of Ian Gallagher. He was a fireman and met Ian through his job when Frank left the gas on the stove on and nearly lit his cigarette. Immediately after they met him, Mandy made a bet with Ian that she could sleep with him first. Mandy lost the bet and Sean was revealed as homosexual. Ian and Sean were unaware that they were related and began a relationship. Ian eventually discovered that they were both children of Gary Bennett when he died and Ian spotted Sean at his funeral. Ian was horrified that he had been having a sexual relationship with his own brother but had sex with him one last time before trying to break up with him, despite the fact Sean had just said he loved him.
Sean was disbelieving at first, pointing out that his father had just died. He refused to believe Ian's simple explanation that he wasn't interested and demanded the truth. However, when Ian explained the situation, Sean wanted to continue their relationship, pointing out that no one else was aware they were related and incest taboos should only apply to heterosexuals, or "breeders", against having children together. Ian completely disagreed with Sean and sadly ended their relationship.
- Matt Cross appears alongside former Shameless star James McAvoy in the 2013 movie Trance.