Conrad Prebys, his son Eric, and the two grandsons. Eric Prebys wrote to his son Jake, explaining the trust.

Billionaire real estate tycoon Conrad Prebys, who died last July at 82, gave hundreds of millions of dollars to nonprofit groups, but he cut his only child, son Eric Prebys, out of the will two years before his death.

By a strange twist of fate, a letter that Eric Prebys wrote to one of his sons, along with Conrad Prebys's Gift Trust #13, got online. A source of mine found them. Eric Prebys wrote to his son Jake, explaining the trust, "As you can see, there are specific clauses exempting me from receiving any money," he wrote. I counted six paragraphs specifically exempting Eric, who had expected to inherit $20 million.

Son, grandsons, Conrad. Eric and Conrad maintained a friendship for 35 years.

"I didn't find out about this until after the funeral," Eric wrote to his son Jake. "I have absolutely no idea what this is about…I didn't know the extent of his animosity until I received the paperwork a few days ago. The fact that he pretended to be friendly when we spoke or when I went out there, now strikes me as downright ghoulish."

In his younger days, Conrad Prebys ran a pizzeria in South Bend, Indiana.

Eric wrote bitterly, "if he'd wasted time being a decent husband and father, he never would have become Conrad the Legend…he had no paternal instincts whatsoever." Each of Eric's two sons got $1 million.

In his younger days, Conrad Prebys ran a pizzeria in South Bend, Indiana. But he was "a drunk my mother had divorced," wrote Eric.

Conrad Prebys came to San Diego in 1965 and prospered as a real estate salesman at the time the market was hot. Then he went on to construction and development. He kept a low profile until he got the philanthropy bug late in his career.

Eric was two at the time of the divorce. At age 16, he went looking for his father and found him in San Diego. There had been no communication after the divorce and Conrad's departure from South Bend. Conrad's "severe drinking problem" was in the past, Eric told me in an interview. "He had been sober for some time." Eric and Conrad had a chat for several hours, and maintained a friendship for 35 years, surprisingly interrupted by Conrad's writing him out of the will.

After he learned that he had been dumped out of the will, Eric started doing some homework -- asking various people about his father's later years and health problems. "I no longer have any bitterness toward my father," Eric told me. "When I wrote the letter to Jake I was very emotional." But he learned that his father had dementia with his myeloma in his later years. "He was not in his right mind. He had an illusion about the animosity." I suspected that Eric might have contested the will and received a settlement, but he would not talk about legal matters.

Eric had some observations about his father. Despite his billion dollars of assets, "he was ridiculously frugal, flew on Southwest Airlines when he had hundreds of millions of dollars. He stayed at a Hampton Inn when he came to see me," says Eric. His Point Loma home was quite nice but not a mansion. "He didn't like to spend money, but late in life he discovered philanthropy. He enjoyed adulation." And how. He gave $100 million to the medical research operation that renamed itself Sanford Burnham Prebys Medical Discovery Institute. He gave $25 million to the Salk Institute which renamed its auditorium "The Conrad T. Prebys Auditorium." He gave $20 million to the La Jolla Music Society, which is building The Conrad Prebys Performing Arts Center. San Diego State University endowed the Conrad Prebys Chair in Bio-Medical Research and boasts of its Conrad Prebys Aztec Student Union. And so on.

Eric Prebys has done well, too. He got a PhD in physics at the University of Rochester, was an assistant professor of physics at Princeton, and is now a senior scientist at the Fermi National Accelerator Laboratory in Batavia, Illinois. He has given physics papers throughout the world, and I admit I can't understand a word of their titles.