When your baby mama starts doing it with a 21-year-old, you can be forgiven for a less-than-pleased reaction.
Such is reportedly the case for Scott Disick, who more or less has to sit by while Kourtney Kardashian and Justin Bieber hook up.
Celebrity Dirty Laundry claims that Scott is distracting himself by hanging out with Kylie Jenner's boyfriend, Tyga, whom the site deems a "bad influence" on Scott.
"In Touch was told by an insider that Scott has been hiding his drinking from Kourtney," the site reports.
On December 6th, Scott was having himself a grand old time while out on the town, and was a "total mess."
The source said that at one point, the father-of-three "pushed his crotch into a girl's face."
Meanwhile, Bieber is L-O-V-I-N-G what this new romance is doing for his self-esteem.
"He has had a huge ego boost from hooking up with Kourt. It's been going on for a few months," a source told People Magazine.
"He is used to being swooned by young girls that have nothing else going on. Kourt is a hot mom with a career.
"He brags about how hot she is."
Both parties are just having fun, the source added, and don't see this as anything more than a fun hook-up.
Bieber is reportedly happy while the whole thing lasts, and can't believe that Kourtney "would go for him."
Believe it, Biebs.
"Even if she is using him to get back at Scott, he couldn't care less," the source said.
"It's just one of those things where it makes Kourtney feel good about herself. It's not serious at all," the source added, pointing out that Bieber has know the Kardashian/Jenner family for awhile.
"This young guy is into her, he thinks she's hot and she's older. She just wants to have fun."