Caitlyn Jenner didn't tell the Kardashian family she was having gender confirmation surgery because she didn't ''trust'' them.

The 68-year-old reality star - who was previously known as Bruce Jenner - revealed in her autobiography 'The Secrets Of My Life' that she had undergone ''the final'' operation in her transition, and though her stepchildren and ex-wife Kris Jenner received advance copies of the book, they didn't get ''the last few pages'', which featured the revelation.

And asked why in an interview for 'Piers Morgan's Life Stories', she admitted: ''I didn't tell anybody [about the surgery]. It's none of their businesses. I had already been living as Caitlyn for a year and a half, OK? I didn't want them to leak it to the press, OK? There was no reason for them to know about it, of course I didn't trust them.''

And the former Olympian admitted she is no longer in contact with her stepchildren.

She added: ''I don't talk to the Kardashians anymore. The only ones I am concerned about are Kendall and Kylie. They are my biological kids. I spent 23 years carting them around.''

Speaking about Caitlyn's claims in her memoir, Kris previously said there were ''two truths,'' adding that for ''more than half the marriage it was like ... perfect.''

And of Caitlyn coming out as transgender, she said, ''I wouldn't have seen that truth in, like, a gazillion years.''

Kris admitted she thought Caitlyn's book was ''very mean-spirited.''

She added that there were ''a lot of inaccuracies,'' and that she wished Caitlyn had simply written, ''Married to her. Didn't work out. She's a great girl.