Alex Rodriguez is revealing some fascinating information about fiancée Jennifer Lopez’s “very close” relationship with Kim Kardashian.

Speaking with People about a new ad for Portal from Facebook that he, Lopez and Kardashian starred in together, the 44-year-old former Yankees slugger discussed Lopez’s longtime friendship with the “Keeping Up with the Kardashians” star.

“We’ve all known each other for a long time,” Rodriguez tells People. “… But Kim and Jennifer are very, very close, and she’s almost like a mentee of Jennifer, and Jennifer’s mentored her a lot over the years. Now they just go back and forth.”

He adds: “They mentor each other and they have this really beautiful relationship that goes back over a decade-and-a-half, and it’s nice to do anything with Kim and our family.”

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According to Rodriguez, he and Lopez regularly get together with Kardashian and her husband, Kanye West, vacationing together and even participating in karaoke nights, telling People that Kardashian is a “really good” singer.

Last year, Kardashian hosted a movie night, and shared video on Instagram in which she called Lopez her “idol.”

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Kim and Jennifer Lopez tonight!

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“My inspiration for everything has been Jennifer Lopez,” she gushed in the video. “I would try and see what shoes she’d wear, what makeup, what hair — I became obsessed with glam because of Jennifer.”

Adds Rodriguez: “We have fun… anytime we see them. To see how much Kim and Jen like each other, respect each other, support each other is awesome.”