The younger generation may consider Rock Brynner's claim to fame is that he was co-founder and namesake of Hard Rock Cafes around the world. (He's no longer a partner.)

To many more, however, he's the only son of Yul Brynner, the actor who spent 35 years off and on in "The King and I" - on Broadway, on film and on tour.Yul Brynner won an Oscar for the 1956 film, the same year he also starred in "Anastasia" and "The 10 Commandments." He was as big as could be for a short time and had occasional hits thereafter ("The Magnificent Seven," "Westworld") but generally wasted his talent.

Rock Brynner is now on tour to tout the paperback release of his unusually good biography of his father, "Yul - The Man Who Would Be King." The book details his father's skyrocket success, steady decline and fusion with his "King and I" role.

During the last several years of his life, suffering from severe back and leg ailments and finally cancer, the actor went on portraying the Siamese monarch to huge box office 50 weeks a year because he couldn't afford not to. When he died in 1985, he disinherited his five children. His estate went to a young fourth wife.

"I'm open to the same charge, I suppose, as the authors of other books by so-called `ungrateful offspring.' But I can tell you, readers have unanimously emphasized to me the love with which this book was written," Rock says. "Yul was an extraordinary, magical and amazing figure.

"I was 5 when he opened in `The King and I' in 1951. He was a very different man in the last two years of his life. The book tries to chart the course of the change in his life. It's a parable of power, how he acquired it and the nature of it and the effect on his life. And finally: Did it bring him happiness? The answer to that is a resounding `no.'

"He was simply not a clean-cut all-American boy. He had an exotic look that limited him in the eyes of studio executives, whom he hated. Also, he was such a pain, people wouldn't work with him twice.

" `Taras Bulba' was a turning point. . . . His own performance was amazing, but everything around it was so lousy. Tony Curtis is a very good actor, but it was his worst performance. Yul had spent years preparing it, but it was butchered before release. When he saw what they'd done to it, he said: `To hell with it. From now on I'll just take the best deal and run.' "

When Rock completes his tour, he'll resume work at Columbia University on his doctoral thesis on the drafting of the Constitution. "I expect to teach American history in college. I have two novels in progress and a screenplay about slavery."