Ain't no Sammy "The Bull" Gravanos in the Bosa family -- 'cause the brother of NFL rookie Joey Bosa says he ain't about to snitch on his famous great-grandpa ... who's a Chicago mob LEGEND.
Joey was just drafted #3 to the San Diego Chargers ... but we spoke with his lil' bro Nick (who's playing for Ohio State next season) and asked about Tony Accardo ... the Bosa's great-grandpa.
Accardo was an uber famous mafioso ... first serving as Al Capone's underboss then eventually rising to all-out boss of the Chicago Outfit in the 1940's.