Jenner was the subject of rumours about his gender identity for almost 18 months before he broke his silence in an interview on Friday.
Speaking to ABC News' Diane Sawyer, he said: "The only real true story of the family was the one that I was hiding and nobody knew it. The one thing that could make a difference to people’s lives was in my soul and I couldn’t share it."
He added that his step-daughter Kardashian and her husband Kanye West were a great support, adding that she had given him fashion advice.
In a preview of the Today Show, Kardashian said that the family had struggled with the change, and with the attention: "I think there is still an adjustment, and there's family therapy, and we're really close," she said
"I see reports that say: ‘This one doesn’t support him’ and: ‘This one’s over here, and [Kris Jenner] feels this way,’ and it’s all really so made up," Kardashian says.
"We all really support him. Is it a hard adjustment? Yes."
The full interview is due to air on Monday.
Jenner admitted that some members of his family were struggling with the change, saying it's “tough on all the girls, I understand that and wouldn’t rush the issue.”
Jenner's ex-wife Kris dismissed "reports" that she didn't support her ex-husband's new gender identity.
Katie Glover, editor of transgender lifestyle magazine Frock told The Independent that families often find it hard to adjust to a "new" member, and that speculation makes it much harder for the person in question.
"Coming out as transgender and then transitioning to the opposite gender is something which very difficult to do," she says. "Often, as soon as people come out, they lose their jobs, their homes and they are shunned by their families and friends."
In the interview, Jenner said that Kanye West gave him inspiring advice. He said: "I can be married to the most beautiful woman in the world, and I am; I can have the most beautiful little daughter in the world, and I have that; but I'm nothing if I can't be me, if I can't be true to myself."
Jenner and Kardashian mostly referred to Jenner using the male pronoun, and The Independent has followed their example.
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