The actor and filmmaker is an Oscar-winning Hollywood legend, but he insists his career achievements all pale in comparison to his personal life, after finding lasting love with Bening, the mother of his four children.

Warren, 79, who was previously known for his playboy reputation, wed the actress, 58, in 1992 and they will celebrate their 25th anniversary next year (17).

"The most important thing that's ever happened - the best thing that's ever happened to me - was Annette and having four kids," he smiled on U.S. breakfast show Today.

Warren was 54 when he finally settled down, and while the marriage news may have shocked some fans of the famed bachelor, he insists it felt like the natural next step after realising Annette was 'The One'.

"It didn't really surprise me," he explained. "I always felt I wasn't trying to avoid marriage, I was trying to avoid divorce. I had no doubt when I met Annette that it was time to get married."

The actor credits a deep, mutual "respect" between the couple for its long-lasting relationship, while he admits using the same approach to their kids' privacy has worked wonders while bringing them up in Hollywood.

"It is a burden, I think, to have two parents that are well-known, so I completely respect their privacy," he continued. "I could go on and on and on and on talking about them, because they're brilliant and fun. But no, I think you have to give them a break, and they have their privacy."

Warren's comments emerge weeks after he publicly praised their transgender son Stephen as his "hero" in a touching interview about the 24-year-old, the couple's eldest child, who was born Kathlyn Elizabeth.

Discussing Stephen's gender identity struggle for the first time with Vanity Fair magazine, Warren said, "He's a revolutionary, a genius, and my hero, as are all my children."

He and Annette are also parents to Benjamin, 22, Isabel, 19, and Ella, 16.