When a babysitter isn't available, call Justin Bieber!
"#Mason & @JustinBieber family pool day!!!" she captioned on Instagram. "#Bestbabysitterintheworld ❤"
For those who haven't been keeping up, the Kardashian family and Bieber have a long history and friendship together.
There's also a special bond Kendall Jenner and Kylie Jenner share with the singer. Whether posing in photo shoots together or hanging out together at mutual friends' parties, the threesome have remained friendly for many years.
And yes, there has even been some possible romance rumors between Bieber and Kendall in particular.
"He's a longtime friend of our family," the Keeping Up With the Kardashians star said in a recent interview. "Everybody loves to assume things, but no….I'm truly focusing on my career."
Don't forget! New episodes of Keeping Up With the Kardashians air Sunday nights at 9 p.m. only on E!