 Born in Ballyhale, County Kilkenny, Fennelly is the member of a hurling dynasty from the locality.His grandfather, Kevin Fennelly, Snr, played with Kilkenny in the 1940s before later becoming heavily involved in the establishment of Ballyhale Shamrocks in 1972.His father, Mick, and his six uncles, Brendan, Ger, Kevin, Liam, Seán and Dermot, all played with the Shamrocks with several of them playing for Kilkenny at all levels.