...and, of course, Sonny handled it in his usual heavy handed way that was discouraging to Vito.
This highlights several inconsistencies in the novel and films: no apparent underboss; when was Vito (or for that matter, any of his boys) made? Why would Vito tell his capos that they could someday form their own families?; Why only two capos? I'm sure that ya'll can think of others.
Heavy-handed indeed. Puzo says that Vito was not entirely pleased because "Sonny was the club, not the rapier."

Inconsistencies? We can spend all day and night on them. Early on, at Connie's wedding, Vito is described as "looking as handsome as the bridegroom in his tuxedo." A bit later, when they visit Genco in the hospital, Dr. Kennedy remarks to himself on Vito "in his ill-fitting tux."