His father Giovanni was a bricklayer who, according to fellow mobster Kevin Weeks, served in the Royal Italian Army during World War I.
In 2000, Flemmi was arrested for moving an arsenal of more than 70 weapons from their mother's shed after learning that it was to be the target of a search warrant.
In October, Flemmi pleaded guilty in U.S. District Court in Boston to 10 counts of murder and accepted a sentence of life in prison without parole.
He made the decision as a part of a deal to reduce the sentence for his brother, Michael Flemmi.
U.S. District Judge Richard G. Stearns said it was difficult to sentence Flemmi, because he had done some good work during his 30 years as a Boston police officer.