While we can talk about how unperceptive Michael was, we should keep in mind his background. No blood relatives - even the rebellious and ambitious Michael - would ever have considered betraying Vito. Michael draws a distinction between "businessmen" and family members as regards loyalty. Even in the bloody world he was raised in, betrayal by a brother was beyond the pale.
Not so sure. Michael knew he was "losing" his family well before he spoke to him mother about the subject after Havana. Recall Mama says "you can never lose your family," and Michael replies, "tempi cambi."
