Actually the Genevese Family have always been the largest/Biggest of the 5 Families (In numbers of Made men anyway) since the beginning.

Turnbull? I did read about Lansky, Costello, Luciano and Gambino's plan to have Vito Genevese set up for drugs so that he can go away for life. This was because they didn't like Genevese's ambition to be the Supreme Mob boss of all USA. And they didn't like the fact that he embraced the narcotics industry. What if this plan of their's backfired? I mean Vito Genevese might have ratted them all out to save his own skin.