All of this is a plot by Nero to take over as Don of his family
- It doesn't seem like Nero has a great relationship with his father. He could be the guy behind the letter to Avilio, initiating a Batman Gambit in which he uses Avilio to kill his father, and possibly the rest of his family. Then, Nero steps in, says he knows who his father's killer is, and kills Avilio, ostensibly as revenge for killing the Don. This then allows Nero to take over as Don with no one else to oppose him, while at the same time getting rid of both his competition and a man who has every reason to want him dead.
- Denied. It was Ganzo.
The fourth person who was there on the night of the murder was someone else in the Vanetti family
- It's been mentioned in the letter and Nero that there was another person who had joined the Vanettis that night. If it was someone who knew them personally and was trustworthy enough to join them then it's possibly another member from within the family. Someone who wants to take out the Don Vincent and his sons by getting Avilio to do the dirty work for them.
- Confirmed. It was Ganzo.
Fio is actually pregnant with Vanno's child
- Vanno is clearly upset over Fio's impending marriage to Ronaldo. Fio makes a comment about Vanno never growing up at her wedding after he gets into a fight with Ronaldo. She tenses immediately when Ronaldo states that her child will help bridge the two families. And despite knowing that Ronaldo plans to kill Nero, she doesn't react until she sees the note carried in the flowers, and then kills Ronaldo. It hints at a relationship between the two.
Any use of spoken English is actually Gratuitous Italian in-universe
It's part of the Translation Convention. So when they say "family" they are really saying "famiglia". This doesn't apply to when they refer to Lawless Heaven.