Although the film portrays quite an age difference between Michael and Sonny, some parts of the novel's content conflicts with that. After Vito defeats Maranzano in 1933 it states that Sonny was 16 and Mike a toddler. However, given other novel information and the film's flasback scene, the timeline has Sonny born in 1917-18 and Mike in 1921. That's just 3 years.
"Generosity. That was my first mistake." "Experience must be our only guide; reason may mislead us." "Instagram is Twitter for people who can't read."
