According to sources, their relationship has been “on and off” for the last few months.
The mum-of-three was pictured at the pop star’s concert in Los Angeles in late March after first sparking rumours they were seeing each other late last year.
"He has met her kids, but they don't hook up around the kids. It's on nights when she has help and is able to go out."
The source added: "Kourtney is great. Justin thinks it's cool that she is older and hot. She isn't clingy and has her own life.
"There are no bad consequences for Justin to hook up with her. She is very easy going and just makes it fun for him to be around her.”
And just last month the KUWTK star donned her shortest skirt and some seriously hot over-the-knee boots to join crowds at the Staples Centre to watch the pop star perform.
Kourt's sister Khloe even took to Twitter the same night to poke fun at her older sibling heading to the concert.
"Is there an age limit on being a belieber? #SeriousQuestion," Khloe asked her followers.
She added: "I am dying at all the replies telling me to ask Kourtney LOL YAAAASSSSS with the shady ways lol. I'm a stan!"
