Rob Kardashian Defends Proposing to Girlfriend in New 'Keeping Up With the Kardashians' Clip

He was seen sparring with his family in a new preview of "Kardashians."

— -- Rob Kardashian's proposal to his girlfriend Blac Chyna was a bit dramatic.

In a new preview clip of "Keeping Up With the Kardashians," which returns to E! for its 12th season on Sunday night, the Kardashian clan's lone son defends his decision to propose to Blac Chyna, whose real name is Angela White, after months of dating.

"Listen to the hostility in your voice," Rob, 29, says to his older sisters -- Kourtney, Kim and Khloe -- in the video. "That's exactly why I don't say anything. It's the first time I ever proposed to someone in my life. Don't come at my with some bulls***."

It appears the sisters weren't aware he had planned to propose to Chyna in front of her family. They found out during a family trip to Vail, Colorado.

Khloe calls the act "so f***** up" in the preview clip.

Rob and Chyna's road to love has been a bumpy one since the two came out as a couple earlier this year. The two run in similar circles and have mutual friends and exes.

Chyna dated rapper Tyga starting back in 2011. The two have a son, King Cairo, whom she had in October 2012. The rapper has since dated Kylie Jenner, Rob's sister.

Rob warns his sisters "I don't want no fighting" in the video. His sister Kim replies in a separate scene, saying, "You make sure that your girlfriend doesn't publicly blast your sisters."

In a separate scene, Khloe says, "The fact that now he wants to be so public blows my mind." She may be addressing Rob's return to the public eye after taking a break from the spotlight.

"He's had a year where he kind of wanted to chill," his mother, Kris Jenner, told E! News back in January. "He hasn't been feeling well and we didn't know why. He was just diagnosed with diabetes, so we're taking care of that. But he's always around."

Jenner added Rob was "depressed" and was focused on his recovery.

The preview clip also shows Kim Kardashian discussing possibly having a third child with husband Kanye West and Lamar Odom's first public appearance since his hospitalization due to a drug overdose last October.