RFK Jr.’s kids aren’t having any trouble “curbing their enthusiasm” for their dad’s girlfriend, CHERYL HINES. They’ve even given the blonde actress a new nickname – “Buzz Kill”!

“Cheryl might as well be wear­ing a ‘kick me’ sign on her back,” said an insider, because Bobby’s kids can’t stand her no matter how hard she tries to win them over.

Bobby Kennedy, 59 – son of for­mer U.S. Attorney General Robert F. Kennedy – was in the midst of a bitter divorce from his second wife, Mary, when he and Cheryl began dating.

Tragically, Mary killed herself in May 2012, soon after Bobby and Cheryl took their romance public.

The couple’s four children – Conor, 19, Kyra, 18, Finn, 16, and Aidan, 12 – “were shattered,” the insider said.

Since then, the kids and several other family members have shunned Cheryl.

“Cheryl desperately wants their acceptance, but there’s no way she’s going to ever win all of them  over,” the insider said. “The kids love their father, but they despise Cheryl.

“Whenever she’s at a Kennedy family function, the kids call her ‘Buzz Kill’ behind her back.”

Still, the 48-year-old former “Curb Your Enthusiasm” star continues to be on Bobby’s arm at family functions, political fundraisers and social events.

In late November, Bobby and Cheryl attended his daughter Kyra’s formal society “debut” in Paris at the Hotel de Crillon. Although Cheryl tried to fawn over the teen, Kyra practically ignored her.

And at a late November Hollywood fundraiser, the source says Bobby’s two older children from his first marriage went out of their way to avoid being seated next to her.

Despite the cold-shoulder treat­ment, Cheryl has no plans to drop her man.

“She turns a blind eye to the family’s resentment,” the insider added. “She’s so crazy about Bobby she’d walk on hot coals to keep him.”