Kendall and Kylie Jenner
Caitlyn Jenner made her relationship with daughters Kendall (right) and Kylie very strained after she released her new memoir. In this photo, the sisters arrive at the 2015 American Music Awards in Los Angeles on Nov. 22, 2015. Reuters/David McNew

The Kardashian-Jenners of “Keeping Up With the Kardashians” are a very tight-knit clan, but after dad Bruce Jenner transitioned into Caitlyn, things were never the same between her and her ex-wife, Kris Jenner.

Her daughters and step-daughters, on the other hand, are a different thing entirely. Kourtney, Kim and Khloe Kardashian kept their distance from Caitlyn, while Kendall and Kylie Jenner made an effort to maintain their relationship with her. But after Caitlyn released her new memoir, “The Secrets of My Life,” even Kendall and Kylie had a difficult time defending her from the rest of the family.

READ: Caitlyn Jenners relationship with the Kardashians strained after sex change

Caitlyn wrote a lot of nasty things about Kris in her new memoir, which made the Kardashians very upset. They naturally sided with their mom, but Kendall and Kylie wanted to stay neutral. Still, an insider told E! News that Kendall’s relationship with Caitlyn has been “very strained,” and she “rarely speaks” to her father now.

“Kendall is loyal to Kris [Jenner] and has very little to do with her dad. The more time that has passed, the more she feels Caitlyn has let her down with the things she has said and with her actions,” the insider said.

As for the youngest of the siblings, Kylie, she is still in contact with Caitlyn. But even she has a tough time sticking up for her dad. “Kylie has really made an effort not to take sides and to be supportive of Caitlyn. She really wants to have a relationship with her dad, but Caitlyn has hurt Kris tremendously and it’s made it very difficult,” the source revealed. “With everyone in the family on Kris’ side, it’s hard on Kylie. She tries to keep it separate and doesn’t want to discuss it with the rest of the family.”

The girls really need their dad, but because of the animosity against Caitlyn, the once-solid bond they enjoyed with their dad is gone. “Both girls really struggle with not being close to Caitlyn,” the source insisted. “It’s left a big void in their lives to not have the father they grew up with. She was a part of their lives every single day.”

This is a really sad development, especially since Kris earlier said she is open to reconciliation with her ex-husband. Even though they divorced in September 2014, they remained on good terms. However, things turned sour when Caitlyn said in a Vanity Fair interview that Kris knew about her transgender tendencies right from the start.

After a few months, the two patched things up. “I’ve really tried to be a good friend,” Kris even told Us Weekly. “I try to be very understanding of how it must feel like to navigate a big huge family.”

“Relationships change all the time… I just try to be a good friend,” she added.