After shocking “Real Housewives of New York” fans earlier this season by saying she’d once made out with her sister, Tinsley Mortimer explained herself during Thursday night’s reunion.

The 45-year-old called the buzzed-about smooch a “joke” on the reunion, prompting host Andy Cohen to ask her, “Tinsley, how does one make out with one’s sister as a joke?”

“So, this was like at least 20 years ago,” Mortimer laughed and explained. “We were doing a joke. I was with a bunch of girls and my sister was one of them and we were saying, like, ‘How do we kiss?'”

She continued, “So we were showing each other how we kissed and so my sister happened to be one of the people that we were both showing how we kiss and it was my sister. It was like two seconds. It’s no big deal.”

Mortimer’s younger sister, Dabney Mercer, has appeared on “RHONY” in the past.

Mortimer made the kissing confession this season during the ladies’ trip to Newport, Rhode Island — before she locked lips with co-star Leah McSweeney.

“Are you a good kisser? Cohen then asked during the reunion.

“I am a good kisser,” Mortimer said as McSweeney agreed.

Unfortunately for “RHONY” fans, the socialite will not be making any more candid confessions. She left the show midway through the season to be with her fiancé, Scott Kluth, in Chicago.

It is unclear when they will tie the knot, as their wedding plans were impacted by the coronavirus pandemic.