Kardashian siblings, Kourtney and Rob, were having fun in their Snapchat this week but the moment gets a bit spoiled when Rob threw a rather unpleasant joke to his momager, Kris Jenner. Is the reality TV star unconsciously showing one of his mood swings again?

In a clip posted in Kourtney Kardashian's Snapchat, the 29-year old reality TV star was seen driving a car while talking to Kris using his phone's loud speaker.

"Hey, Mom. Why don't you shove your d--k in my mouth?" he said in the clip posted on Monday, August 8.

It can be heard that the momager sounded confused and had kept saying 'Yeah?' while Kourtney and Rob were boisterously laughing.

The Kardashian sister went to the rescue jokingly saying, "There's something so wrong with my brother, I just want you guys to know that."

The clip came in the heights of reports that the Kardashian brother is in a crisis balancing his schedule while filming his own six-episode reality TV show with pregnant fiance, Blac Chyna.

In reports, Rob is said to have 'skip and not show up' in several taping sessions.

"He's struggling to readjust to the grueling work schedule."

In another report, it was said that filming of the show had been suspended for weeks due to the celebrity's uncooperative behavior.

"Rob has refused to film for weeks... You can't make Rob do anything. He isn't worried about contacts, and it's become a waste of time for everyone."

The source also said announced that the socks entrepreneur also have a hard time keeping a balance working on his new reality TV star and being with his pregnant partner.

"It was like a honeymoon every day with Chyna before filming started. But working with your pregnant partner and living together has been stressful. Rob just shuts down," the source said.

Last month, Rob is said to have been in his 'dark periods' and was 'depressed' as he deletes a lot of photo in his Instagram and unfollowed his bride-to-be.

" He goes through his dark periods. He gets depressed and doesn't want to really do anything, doesn't leave the house. It got better for a bit when he first started dating Chyna, but he's in a rut now. He'll snap out of it," a source said.

Meanwhile, the split rumors for Rob Kardashian and Blac Chyna may rest for now as both of them uploaded a loved-up video in Snapchat.

As for Rob and Kris Jenner, the 29-year old previously showed his sweet side to his momager by sending her a gift after the latter was involved in a car accident off Highway 101 in Los Angeles on Wednesday last week.