Complex sentence: His father, John Tunney, and his uncle Frank Tunney were promoters of wrestling in Toronto and all over southern Ontario, and what they didn't promote, they still had control over, allowing small promoters to run small towns where it suited them.
Split into simpler sentences: His father, John Tunney, and his uncle Frank Tunney were promoters of wrestling in Toronto and all over southern Ontario. What they didn't promote, they still had control over, allowing small promoters to run small towns where it suited them.