Marini was born in Charleston, South Carolina. His parents were Italian immigrants from the region of Trentino. He graduated from Fairless High School in Navarre, Ohio. His father, Lou Marini Sr., was the high school's band director and wrote the school song. Fairless bestows the annual Lou Marini Award in honor of Marini Sr. who died in May 2008. Both Lou Marini Sr. and Lou Marini Jr. were inducted into the Fairless Alumni Association Hall of Honor in May 2010. In June 2010, Marini Jr. was named artistic director at the first Brianza Blues Festival, in Villa Reale (Monza, Italy).