Carole Cancels Upcoming Plans Amid Mother-In-Law's Death: 'They Were Very Close'

Carole Radziwill has canceled her upcoming plans in light of her late mother-in-law's passing, RadarOnline.com can exclusively reveal.

Whiles sources tell RadarOnline.com the ex Real Housewives of New York star is "holding up really well" after Lee Radziwill died at 85, she's making an effort to "lay low" by "spending time with close friends."

Carole broke the tragic news in a touching tribute on Sunday night.

“She was loved. Rest in Peace, Lee. Thank you for the kind words & comments,” the former reality star said as a caption alongside a black and white photograph of Lee.

As readers know, Carole was married to Lee’s son, Anthony Radziwill, who died from cancer in 1999. The former reality star’s late husband’s death came just weeks after his cousin, John F. Kennedy Jr., died in a plane crash.

"They were always close and shared a very normal relationship," an informant revealed exclusively RadarOnline.com about Carole and Lee's bond.

"Lee was the final connection she had to Anthony, so of course it's sad."

Lee was best known as Jackie Onassis' younger sister and the sister-in-law of President John F. Kennedy. She was also a former socialite and interior decorator.

Meanwhile, Carole is keeping busy with working on her own scripted series, said the pal, adding she's "still very happy she left RHONY" because "last season did a number on her."