Celeste Anne Morello managed too interview one of the oldest members in the Philadelphia crime family, Harry Riccobene. Her work was reliant on his testimony and is called "Before Bruno". In it, Ricobene reveals that what would become the philly mob was actually 3 mafia families put together. All three came from different parts of Sicily. each having 30 made members. Until the Gambino family organized it under the leadership of its first boss, Salvator Sabella.

As noted in "blood and honor: Inside the scarfo mob", and "mafia prince", the Calabrian Italians were noted as a faction in the philly mob. They held alot of autonomy and secrecy, a family within the family if you will. And its leader, Antonio caponigro would go on too kill and usurp the boss position from Angelo Bruno.

All this is too say that, The families we now see in new york, chicago, philly, and new jersey were likely not one cohesive group, but many separate crews/families that fought for dominance. This is likely how the largest of the five families, the Genovese, were formed. in Selwyn Raab, book "Five Families: The Rise, Decline, and Resurgence of America's Most Powerful Mafia Empires" raab describe Joe the boss as an xenophobe who refused to deal with non Sicilians. Yet was known for his brutality and expansion during the prohibition era. as noted by selyn swab...

"Masseria’s success stemmed partly from a keen eye for talent to run andprotect his rackets. Three of his brightest young recruits, who had emigrated as boys to America, Salvatore Lucania, Francesco Castiglia, and Gaetano Lucchese."

Another way a family was formed was because gangsters, and their family members reverted too sticking with their fellow Sicilians clansmen from the homeland. selwyn swaab noted that the castelemares Sicilians stuck together and created a very powerful Borgata.

"In addition to the Castellammarese overseas clan, several other loosely organized Sicilian gangs, some with southern Italian members from the Naples region, were thriving in New York by the late 1920s, mainly due to bootlegging."

"In 1930 other members of the Castellammarese Borgata turned to Maranzano for guidance and leadership"

"Joseph Bonanno, who would create a Mob empire in America. Bonanno, whose father and close relatives were sworn mafiosi, came from Castellammare del Golfo"

The rural and disparate area of Sicily made it so that regional families were powerful where they operated, but in new York, everyone was a hairs breath away. And with the introduction of prohibition, made it so expansion/domination or teaming together for help/ co-operation, very lucrative for those on top.

Given this, how did the families maintain themselves with all these different factions together? The recognition of the rules that guided it. As noted by joseph Pistone in his book "Donnie Brasco: My Undercover Life in the Mafia"

"It wasn’t the toughness of an individual that caused the fear so much. It was the structure. It was the system of hierarchy, rules, and penalties that can terrify the toughest wiseguy in the business. The more potent toughness is in the ability to enforce the rules."

Simply speaking, enough people, right people, recognize the authority in the bosses, captains and soldiers of the family to make the whole thing work.