There are many things that Justin Bieber has been named as during his short career, but so far the term ‘best babysitter’ hasn’t ben one of them… Until now.

At a recent family pool party, the Kardashians invited the 21-year-old round for a swim, and it appears Kourtney Kardashian’s 5-year-old son Mason took a shine to the troubled pop star.

Kris, 59, shared a snap of Justin giving Mason a piggy-back in the pool on her Instagram page.

She then wrote beneath it: “#Mason & @JustinBieber family pool day!!!#bestbabysitterintheworld #Repost @justinbieber. Mason is cool as a fan.”

Justin is good friends with Kris’s daughters Kendall an Kylie Jenner, with a recent American magazine dubbing them as ‘Hollywood’s new brat pack’.

Kris’s followers were quick to question her judgement on the ‘best babysitter in the world’ tag, with one fan writing: “In the world Kris? Really? Think about what you're saying.”

Justin has been keeping a fairly low profile since his arrest for driving whilst intoxicating last year in Miami.