You are wrong. He was not an heir at all. Yoko got EVERYTHING. John died without a will and it all goes to the wife unless otherwise stated. She gave Julian $100 a week when John died and 14 years later settled for less than a million.
You seem to know a lot about Julian's situation, but your statement above is wrong factually and legally. You can see an image of John's will at the bottom of this page. It leaves everything to Yoko.
It would have been much better for Julian if John had not had a will because Julian would have received 1/4 of John's estate under New York's intestacy laws. Plus, Julian wouldn't have to live with the knowledge that his father intentionally excluded him.
The 100k that has been mentioned was from the divorce settlement. I believe I read somewhere that the bitch Yoko has thrown Julian a bone or two since then, but not much.
I also read in Cynthia's book that at the time of John's death Yoko told Julian while he was in NY for the funeral service that he could pick out one of John's guitars. Julian, who was a guitar player at the time, was thrilled and chose the one he had always cherished. Yoko said he couldn't have that one because she was going to give it to Sean, which broke Julian's heart more than it already was.
I'm glad to hear that Julian is close with Sean. Hopefully, when the bitch assumes room temperature Sean will do something to correct the inequity perpetuated by his mother.