Billy Joel's third marriage is breaking up, but he says it's not because his wife has been stepping out with a dashing designer.

The "Piano Man" and wife Katie Lee confirmed the split to The New York Daily News in a joint statement: "After nearly five years of marriage, Billy and Katie have decided to separate.

"This decision is the result of much thought and consideration. Billy and Katie remain caring friends, with admiration and respect for each other."

Rumors have swirled for months that the marriage was on the rocks, with reports linking Lee, a 27 year-old chef and author, to Yigal Azrouel, a handsome 36 year-old Israeli-born fashion designer.

Sources reported seeing them dirty-dancing in Miami in January and have claimed that Azrouel referred to Lee as "my girlfriend."

Reps for the Joels insisted that Azrouel is just a friend and that Billy, 60, was happy to skip the parties, fashion shows and fund-raisers that his younger wife enjoyed.

"Their decision to separate was absolutely unrelated to Yigal," said Joel's spokeswoman Claire Mercuri.

"It was really the age difference that caught up with them," said a friend of the couple. "They grew apart. She is very career-oriented. She loves going out. She loves the city. When Billy isn't touring, he'd rather be on Long Island with his motorcycles and boats."

Various friends hinted at infidelity on both sides, though a longtime pal of Joel insisted "he's always remained faithful to Katie. When he was touring with Elton John, he flew home almost every night."

In recent weeks, Joel has been living on Long Island, where he owns mansions in Sag Harbor and Sagaponack. Lee is said to have stayed at the couple's Greenwich Village townhouse, not far from Azrouel's boutique.

Joel's daughter with Christie Brinkley, Alexa Ray Joel, told The New York Daily News she knew about the divorce.

"Of course. I was the first person he told," said Alexa, who is just four years younger than Katie. "He's doing very well. ...I am going to help him and I am going to be there. It's for the best."

Lee, who grew up in West Virginia, met Joel at a New York party in 2003 and they married a year later. Alexa was maid of honor.

Joel's nine-year marriage to model Brinkley ended in 1994. His nine-year marriage to Elizabeth Weber went bust in 1982.

For his latest marriage, he's believed to have a prenuptial agreement to protect the millions his many hits have made him.

"This decision is a result of much thoughtful consideration. Billy & Katie remain caring friends with admiration and respect for each other," Joel's publicist said in a statement.

Grammy Award winning Joel, whose hit songs include "Piano Man," "Uptown Girl," and "An Innocent Man," has sold more than 150 million albums worldwide and been inducted into the Rock and Roll Hall of Fame.

"I was very sorry to hear this news," Brinkley told "Entertainment Tonight." "I wish him the very best. I wish them both happiness in their future. Billy's a great father, and he's been a great friend to me over the years."

"Entertainment Tonight" caught up with Brinkley - who was married to Joel from 1985 to 1994 - Wednesday night at a Manhattan event for the Wayuu Taya Foundation.

At the same event, Brinkley's daughter with Joel, Alexa Ray, told "Entertainment Tonight": "He's a classy man. He will handle this beautifully, as he handles everything. I am behind him 100 percent and supportive of him. Me and my Dad are very close."

Alexa Ray also told Us magazine that she "wasn't surprised" when she heard the news. "I have a pretty good women's intuition, so I can tell," she said. "I know my dad pretty well, so I'm behind him."

The interviews will air on "Entertainment Tonight," Thursday night.

"I was the first person that he came to [with the news]," she told UsMagazine.com Wednesday at the 6th Annual Wayuu Taya Foundation Gala in New York City. "You can't just trust everybody, and I like knowing that my father can talk to me in the same way that I come to him. I'm just supporting him right now."

Reports have linked Lee, 27, to 36 year-old Israeli-born fashion designer Yigal Azrouel, who has frequently escorted her to events. But a source tells Us that "had nothing to do" with the split and that Joel, 60, and Lee had just grown "apart" after five years of marriage.

Alexa Ray tells Us Magazine she "wasn't surprised" when she heard the split news.

"I have a pretty good women's intuition, so I can tell," she said. "I know my dad pretty well, so I'm behind him."

Alexa Ray's mother Christie Brinkley went through a rough divorce last year with ex-husband, Peter Cook.

So have her parents' rocky love lives changed her views on marriage?

"I am a true romantic - I would love to get married," Alexa Ray told Us Magazine. "The government doesn't necessarily have to get involved. You can just celebrate your life and have a wedding and have it big and fabulous and not necessarily complicated, with the papers and all that. Having seen what I've seen, I'll be skeptical, sure, but I will be having a wedding."