I think that Cain was brought in by Pat Marcy during the early 1950's and the FBI considered him as a made member. He was also direct with Giancana,Marcy and another guy from the Capone era and member of the First Ward, Buddy Jacobson.

Mongol General: Conan, what is best in life?

Conan: To crush your enemies, see them driven before you, and to hear the lamentations of their women.