John Feehan, Chief Executive, said : "This is a very sad day for Rugby, Nevin was a rising star for his province and his country. He will leave a lasting legacy with the Rugby Community in Ireland."
RaboDirect PRO12 Chairman Andy Irvine said: "The news of the tragic deaths of the Ulster player Nevin Spence, his father and brother on Saturday has hit the rugby community hard around the world. Our thoughts and prayers are with his family and friends at this terrible time.
"Nevin made his debut in the RaboDirect PRO12 in the 2009/10 season and scored four tries in 33 appearances for Ulster in the tournament.
"He was one of a fine crop of young players coming through the ranks at Ravenhill and had earned age group honours as well as playing for Irish Wolfhounds. He was undoubtedly an Irish international in the making.
"It will take time for the Ulster players, management and fans to come to terms with their loss and the RaboDirect PRO12 has been robbed of one of its rising stars."
RaboDirect PRO12 will liaise with Ulster Rugby with regards to the next round of matches and will respect the wishes of Nevin's family and teammates.