Caitlyn Jenner has become distant with "a couple" of her children since she came out as transgender.
The former Olympic champion first revealed she had transitioned to a woman two years ago and has said that since then she has seen some of her children drift away from her.
Jenner, 67, has six biological children - Burt and Cassandra with first wife Chrystie Scott, Brandon and Brody with second wife Linda Thompson, and Kendall and Kylie with third wife Kris Jenner.
She was instrumental in raising Kris's children from her first marriage - Kim, Khloe, Kourtney and Robert Kardashian,
In an interview with Diane Sawyer on news show 20/20, Jenner said the children still call her "Dad" and added the reality of her transition has been difficult.
She said: "Some [of my children] I have remained very close to. A couple of them ... I'm a little more distant.
"I have to admit, I'll sit here and wonder, 'Is it because of my transitioning? Or is it because their life is so busy that they don't call, like, all the time?'"
She continued: "Nobody calls that much. I mostly reach out to them. Obviously the Jenner side calls more, but they all have their own lives."
Jenner also admitted some of the children had doubts about her debuting her new identity in a corset on the cover of Vanity Fair in June 2015.
She said: "My feeling on that picture, I know, my kids that thought, 'You know what? It's a little too much', but from my standpoint, I had suffered for 65 years, okay?
"To have a beautiful shot of my authentic self was important.
"And the shock value... I wanted to end the old Bruce, my old life. And that picture did it."
Jenner was speaking to Sawyer as she promotes her new autobiography The Secrets Of My Life.
However, her ex-wife Kris has spoken of her distress over what she claims are "made up" details in the book.
Kris, 61, refutes Caitlyn's claims that she was aware of her desire to transition into a woman throughout their relationship and before they "made love" for the first time.