I imagine Rocco and Neri might have had an unspoken competition to gain Michael's favour - obviously Neri won that one.
I agree. Michael was possessive: Rocco was Clemenza's protege, Neri was his. I think that's part of the reason that, when Michael gave the order to have Roth's plane "met," he turned to Rocco, not Neri, for that near-certain one-way mission.
As for Tom, it wasn't necessary. Don Vito considered him a son. That was enough.
That was enough when Vito, Tess and Clem were alive. Tom was raised in the Corleone home as Vito's son and Sonny's brother. Tess and Clem probably looked on Tom as a "nephew," or even a godson. They took orders from Tom because he was conveying them from Vito, whose policy was to give criminal orders to one person at a time--the better to avoid creating "corroborating witnesses" if someone turned rat.
But, Michael had no such familial feelings for Tom, and Tom's status with Michael was never certain. Yes, at Connie's weddig he introduced Tom to Kay as "my brother." Then he demoted Tom after he took over as Don. At Anthony's party in II, he tells Ola that Tom is "my lawyer," and he won't sit in on the Cuba negotiations with Ola, Neri and Rocco. After the Tahoe shooting, when he said to Tom, "You're my brother," Tom practically broke out in tears and replied, "I've always wanted to be thought of as a brother, Mike," meaning that he must always have been in doubt about it. The Master Manipulator put Tom in charge while he was away, so, Neri and Rocco took orders from him. But, Michael shouted in anger at Tom as soon as he got back. And, in the penultimate boathouse scene, he humiliated Tom in front of Rocco and Neri. Look at the smug look on Neri's face when Michael confronts Tom about an offer he got from the "House and Hotels," and tells him he can take himself, his family--and his mistress--to Vegas. Seems to me Neri was the source of that information
