One interesting wrinkle would occur when Neri joined the family and eventually became a special jobs guy. This is where Luca could begin to feel left behind.
Pete, I don't see any potential conflict. As the novel explains it, Luca chose to be commanded by Vito regardless of any other variables. I don't think he would have been concerned about Michael's adoption of Neri nor about any ranking in Corleone family.
"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."
