Justin Bieber Babysits Kourtney Kardashian's Son Mason Disick

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Photo: Instagram
According to momager Kris Jenner, Justin Bieber is the "best babysitter in the world" when it comes to looking after her grandson Mason Disick.
Justin, Kris and Mason's mom Kourtney Kardashian all posted the same pic of Justin playing in the pool with the five-year-old reality star. "Mason is cool as a fan," the 21-year-old singer Instagrammed.

Kris added upon re-Instagramming: "#Mason & @JustinBieber family pool day!!! #bestbabysitterintheworld."
Bieber has been spending quite a bit of time with the Kardashian-Jenner clan. He was just recently photographed with Kendall Jenner inVogue's "Brat Pack" spread and has snapped quite a few selfies with Kris.

It seems pretty inevitable that he'll show up on an episode or two of Keeping Up with the Kardashians.