Kylie Jenner and Kourtney Kardashian hung out with Rob Kardashian's ex-girlfriend, Adrienne Bailon.

Us Weekly reported that the two "Keeping Up with the Kardashians" stars spent time with their brother's ex-girlfriend. Kylie Jenner and Kourtney Kardashian also took to Instagram on Sunday, Feb. 28, to share a photo of their get-together.

"Cause we are sistersss," Jenner wrote. "Reunited best friends lol," the eldest Kardashian sister posted.

Adrienne Bailon and Rob Kardashian were together for two years. They broke up in 2009.

The publication added that the actor admitted that he cheated on her in a 2010 episode of "Keeping Up with the Kardsahians."

Meanwhile, the reclusive "KUWTK" actor has declared himself an orphan. According to News.com.au, Rob Kardashian has been at odds with his family since his relationship with Blac Chyna was revealed.

"When the p---y good but your family don't like her so you drop your family and become an orphan [sic]," Kardashian posted on Instagram.

News on Rob Kardashian and Blac Chyna's relationship was confirmed last month after the model posted a photo of herself with the actor's tattooed arm wrapped around her.

YHM reported that Rob Kardashian and Blac Chyna's relationship is getting him in trouble with his sisters. Khloe Kardashian is said to feel "majorly betrayed" while Kylie Jenner is purportedly "livid" over the news.

Blac Chyna is the ex-girlfriend of Kylie Jenner's current boyfriend, Tyga. She and the rapper have one son together.

Last month, Rob Kardashian posted a photo of his lady love with the words: "Blac Chyna probably out shopping [right] now as she [plans] to give birth to the only next generation of the Kardashian Name! #BabyKardashian"

The Hollywood Gossip noted that the actor is so enamored by the model that she already has major control over his life.

"Rob is letting her take control of whatever she wants. She is his queen," an insider said.

"She is helping with the decorating and the new pieces in the home. They haven't moved in yet, but will very soon."