Lettieri's grandfather, Lou Nanne, played, coached and was the general manager of the Minnesota North Stars. His father, Tino, played professional soccer, while his uncle Marty Nanne was drafted 161st overall by the Chicago Blackhawks in the 1986 NHL Entry Draft and played in the International Hockey League (IHL) for three seasons. His cousins are also ice hockey players – Tyler Nanne was drafted 142nd overall by the New York Rangers in the 2014 NHL Entry Draft, while Louis Nanne was drafted 188th overall by the Minnesota Wild in the 2012 NHL Entry Draft.