Robert F. Kennedy Jr. Cheats on Cheryl Hines?

ROBERT F. Kennedy Jr. has been cheating on fiancee Cheryl Hines!

According to a new report, RFK has been two-timing Cheryl with a wealthy Connecticut socialite!

The woman is a 42-year-old mother of four who is estranged from her husband, and sources say Kennedy preyed on the shapely brunette at their gym.

“Bobby was well aware that she was going through a bitter divorce, and he took advantage of her at a very vulnerable time,” a source told American tabloid the National Enquirer.

“Like he’s done with numerous women before, he turned on the Kennedy charm to woo her into the sack. He’s a no-good horndog,” the source added.

Insiders say the woman didn’t realize Kennedy, an attorney and environmental activist, was seriously involved with Cheryl, 48, and only recently learned that he planned to marry the actress at the Kennedy-clan compound in Hyannis, Mass., this summer.

“She’s been terribly hurt by being led on by Bobby,” said the source.

“She really liked him, but now realizes he’s a cad for giving her false hope that they might have a future together. He’d even hinted that marriage was a possibility.

“Despite being involved with Cheryl, Bobby had the woman fly back home with him on the same plane. He didn’t care about being caught.

“Now the woman has become just another notch on his belt. It’s particularly awful after the pain she’s been going through with her divorce.

“If Cheryl Hines has any sense, she’ll head for the hills before she walks down the aisle with this guy!”