Kylie Jenner has totally changed her tune when it comes to her brother Rob Kardashian's relationship with his fiancee, Blac Chyna.
A source close to the brother and sister tells ET that although Rob's new relationship was initially "tough" for Kylie given Chyna's various ties to the Kardashian family, she acknowledges how happy he is and doesn't want anything to change that.
"Kylie is over the relationship," the source says. "It was tough for her in the beginning. But she sees how happy he is and all she wants is for him to be happy. The general consensus in the house is 'Praise Chyna! Don't go!' They finally got the brother they always knew back."
WATCH: Kardashians Call Rob's Engagement to Blac Chyna 'F**ked Up' in Explosive 'KUWTK' Season 12 Promo
According to our source, the entire family is pleased to see Rob doing so well.
"He's never been this happy," the source says. "The entire family is so happy for him and are over the initial shock of their relationship, especially how quickly it started and escalated."
Kylie, 18, and Chyna, 27, publicly squashed their rumored feud late last month, when Kylie Snapchatted a selfie of the two together. "When we've been best friends the whole time ..." she wrote.
"So happy my girls finally got to talk and make peace! #MyFamily #AllLove" Rob later captioned another pic of the pair on Instagram.
Since then, Rob has been spending time with his younger sisters, recently Snapchatting a fun day with Kylie and Kendall hanging out at Caitlyn Jenner's house.
Although, on this season of Keeping Up With the Kardashians, it's no secret that the family initially had plenty of issues with Rob's relationship. On the season 12 premiere, which aired Sunday, Khloe Kardashian revealed the shocking way she found out that Rob and Chyna were dating.
"Do you want to hear the craziest story?" Khloe asked Scott Disick on Sunday's episode. "Rob was asking what time I would be home and [when] I got home 30 minutes earlier than the time I told him I was coming home, I walked in on him with Blac Chyna at my house."
"There was alcohol everywhere," Khloe continued, confirming the swirling reports from earlier this year that she was blindsided and angry to find them together. "He's having the time of his life. I don't need this s**t. Don't you dare make me feel uncomfortable in my own home."
In last week's season 12 promo, Kim Kardashian West also had no problem airing out her displeasure.
"He proposed in front of her whole family," Kim said, as it appears the family found out about the pair's engagement on the Internet. "That's so f**ked up."
"You make sure that your girlfriend doesn't publicly bash your sisters," Kim also told Rob on speakerphone.
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Still, when paparazzi caught up with Rob last month in Los Angeles, the 29-year-old reality star insisted that his famous family were all for his engagement. Rob proposed to his girlfriend of two months while the entire Kardashian clan was away on vacation in Vail, Colorado.
"My family is very happy," Rob confirmed when a reporter from X17 asked if his family is upset that he's planning to say "I do" to Chyna.