Poppinga comes from a very athletic family. His father, Dennis, played as a tight end at BYU from 1968 to 1971; his brother Casey played the same position at Utah State University and appeared on the practice squads of the Seattle Seahawks, the Kansas City Chiefs, and the Philadelphia Eagles during the 2004 NFL season; his brother Kelly played linebacker at BYU, signed with the St. Louis Rams, and now is the linebackers coach at the University of Virginia; and his older sister Tara played volleyball at Utah State.