There's more drama than ever when it comes to the new season of Keeping Up With the Kardashians.

Chief among them is 29-year-old Rob Kardashian's long-awaited return to the show, when his sisters confront him about his engagement to model Blac Chyna. The couple got engaged earlier this month, after three months of dating. Rob's timing was notable, given that he proposed while his entire family was away on a vacation in Vail, Colorado.

Obviously, the Kardashian sisters aren't thrilled with the big news.

WATCH: Kris Jenner Calls Out Kim Kardashian for Being Judgmental: 'Married for 72 Days! Really, That's Normal?'

"He proposed in front of her whole family," Kim says, as it appears the family found out about the engagement on the Internet. "That's so f**ked up."

Kim also confronts Rob on the phone, as a nervous-looking Kylie stands in the background.

"You make sure that your girlfriend doesn't publicly bash your sisters," Kim tells Rob on speakerphone.

Things eventually come to a head when Kourtney, Kim, and Khloe have a sit-down with their younger brother.

"Listen to the hostility in your voice, that's exactly why I don't say anything," Rob testily tells his older sisters. "It's the first time I've ever proposed to someone in my life -- don't come at me with some bulls*it."

Other topics being addressed on season 12 of KUWTK is Khloe's ex, Lamar Odom, making his first public appearance at Kanye West's Yeezy Season 3 Fashion Show in February since almost losing his life in October, and Lamar also meeting Caitlyn Jenner for the first time since her transition.

"What's happening? We got to talk!" Caitlyn tells a clearly uncomfortable-looking Lamar over a family meal.

WATCH: EXCLUSIVE: Lamar Odom Opens Up About Khloe Kardashian Divorce -- 'We've Been Through a Lot'

Last month, Khloe talked about the confusing time when Lamar first met Caitlyn on an episode of her now-canceled FYI show, Kocktails With Khloe. Khloe admitted that she was very protective over the former NBA pro's state of mind.

"When he had his accident and he was in the hospital, Caitlyn was like, 'I want to come and see Lamar,'" Khloe revealed. "Lamar did not know about Caitlyn at that time."

"So, when Caitlyn wanted to come and visit Lamar for the first time was in the hospital, I wanted to respect Caitlyn being Caitlyn, but I also was like..."

A source told ET that the meeting ultimately occurred "a little less than two months" after Lamar returned to Los Angeles.

"I'm not sure if he entirely understood what was going on, but Lamar is very open and non-judgmental," the source said. "He would be open and understanding regardless."

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