Reinhart was born in North Vancouver to Theresa and Paul Reinhart. His father, Paul, was a National Hockey League (NHL) defenceman, and is now a stock market financier and promoter. Reinhart wears the jersey number 23, the same number that his father wore in the NHL. Sam has two brothers: Max and Griffin. Max was selected in the third-round in 2010 NHL Entry Draft by the Calgary Flames and plays in their organization. Sam played alongside Max on the Ice's Ed Chynoweth Cup-championship team in the 2010–11 Western Hockey League (WHL) season as well as the 2011–12 season. Griffin was selected fourth-overall in the 2012 draft by the New York Islanders, and has played against Sam's Ice with the Edmonton Oil Kings in the WHL since 2011–12.