some that come to mind off top are

- Cesare Bonventre (Bonanno) who was made Capo of Sal Catalano's crew somewhere around the age of 26-28. im not sure why Catalano moved on from his crew. I think it was either law enforcement pressue / Pizza Connection, or because he was promoted to acting boss for a brief time after Galante got killed (and IIRC he had to step down due to language and communication issues). Either way Bonventre was made Capo and was one of the youngest capos, if not the youngest, in post-Appalachin LCN history

- Alphonse Trucchio (Gambino) made Capo at 30 years old or a little younger

- Ronnie Giallazano (Bonanno) made capo under 40 years old and I believe he was acting capo before that for a minute, before he went to prison in the early/mid 2000s. Not sure if he inherited his uncle's crew or what the lineage of that crew was. Howard Beach / Ozone Park , huge crew, lots of associates. i think it was Asaro, Asaro's son and then Giallanzo?

- Greg Scarpa Jr (Colombo) . In the book Mafia Son it says Scarpa Jr was a Capo, running a crew separate from his fathers crew. when he was in his 30s. not sure if this was true, or if the author just called him a captain when he was really a solider in his dad's crew, commanding a ton of young associates under him. He had a big pot dealing ring on Staten Island, lots of young kids working for him. That book also said he officially outranked his father, which i think was total bullshit

- John Baudanza (Lucchese) was an acting capo in his 30s. not sure which crew, maybe his father in law's..which would mean essentially the old Vario crew

Alphonse Trucchio being capo at that age is the most astouning, because his crew was massive and into pretty much everything. one of the most active crews in NYC, definitely the most active and biggest crew in Queens. They had him on tape (an informant was there wired up) at a meeting in NJ sittint with big time guys like John Gambino and the Philly Bosses. he was definitely a "rising star" before he got locked up