Caitlyn Jenner hints just how sour her relationship with Kim Kardashian has become.

Caitlyn Jenner has opened up about her relationship with her children, revealing that she hasn’t spoken to Kim Kardashian in “a long time”.

Appearing on the Today Show on Thursday morning to talk about her memoir, The Secrets of My Life, Caitlyn appeared uncomfortable when asked about comments Kim made on the Ellen DeGeneres show in April labelling parts of the book “not truthful”.

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Kim had told Ellen that she felt like Caitlyn was not being honest about “certain things with my mum”.

The transgender advocate told Today Show hosts Karl Stefanovic and Lisa Wilkinson that she loves Kim, and that they have a “very good relationship” but conceded she hasn’t spoken to Kim about the concerns she voiced while on Ellen.

“Well, to be honest with you, I really haven’t talked to her in a long time. I’ve kind of let everything calm down.”

“So I kind of stay – you know I keep my distance. I’m out right now trying to make a difference in the world.”

The 67-year-old said the book was a chance for her to voice her opinion, saying that her view had been absent on the family's claim-to-fame TV show, Keeping Up With The Kardashians.

"See, if anybody did watch that show for the last, it's been 10 or 11 years now, they always saw me in the background because I have a bunch of very strong women in my life. My opinion in the show was like zero," she said.

"This book is my book about my opinions in life and my opinions on issues and things that had happened with me and my family.

"Anytime I express my opinion, you know, with my family, there's always challenges in doing that."

Caitlyn said she was proud of the book and made no apologies for its content.

"It's extraordinarily honest. I even say at the beginning of the book there are different opinions here, but this my story. Not theirs."

The former Olympian went on to say that her relationship with her all her children, including her six genetic children, is good.

"Going through this (transition from male to female) I would say some, we have become much closer after everything I've been through over the last three years. There's some of them that maybe not as close."

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"When you have this many kids, every experience and every relationship is different."

When pressed by Karl about her relationship with Kim, Caitlyn only said "I love Kimberley."

"We have a very good relationship. She has been very good with me."

"There is a lot of drama the Kardashian family, so, yeah, I know that's shocking to everybody," she joked.

"I love all my children including Kim. She's been great."