 Born in Ballyhale, County Kilkenny, Fennelly was brought up in a family that had a strong association with hurling.His grandfather, Kevin Fennely, Snr, played with Kilkenny in the 1940s, while his uncles - Brendan, Ger, Kevin, Jnr, Liam and Seán - all played for Kilkenny from the 1970s until the 1990s

Fennelly first played competitive hurling at juvenile and underage levels with the Ballyhale Shamrocks club.After much success in these grades he later won three All-Ireland medals with the club's senior team.