 Reilly is the younger brother of current New York Rangers defenseman Brendan Smith and National Lacrosse League (NLL) player Rory Smith.The three all played minor hockey in the Etobicoke neighbourhood of Mimico with the Faustina Sports Club, then all played for the St. Michael's Buzzers minor juniors.Smith faced his brother Brendan in the Eastern Conference Quarter-finals of the 2014 playoffs when his Bruins faced Brendan's Detroit Red Wings; the Bruins ultimately won the series four games to one.