Leo and Ignacious are somewhat based on two of the six Lanzetta Brothers, 1920s Philadelphia gangsters. Leo was the leader of the family and Ignatius (spelling difference from Boardwalk Empire character) were heavily involved in the numbers racket, as well as bootlegging.
Their bootlegging was of a different variety than the typical Atlantic City method of bringing it in by sea. The Lanzetta brothers would provide people who lived in tenements with the raw materials to distill liquor and then buy the finished product. With this method, the brothers remained impervious to prosecution since the "Alky cooks" wouldn't rat on them if caught. Known for their ruthlessness, the threat of violence was enough to keep the brothers one step from the law in such instances.