Bruce Jenner is "transitioning into a woman".
The 'Keeping Up With The Kardashians' star is said to be "happy" and "in a great space" after a source close to the family confirmed rumours he has decided to live as a female.
The insider said: "Bruce is transitioning into a woman.
"He is finally happy and his family is accepting of what he's doing. He's in such a great space. That's why it's the perfect time to do something like this."
The former Olympian, 65 - who sparked speculation he had started the transition after appearing with longer hair and wearing makeup over the past few months - is said to have recorded his own reality show documenting his progress, which will air when he is ready to share his journey.
The source said: "It will air when he is ready to be open about his transition.
"But he's acting more and more confident and seems very happy."
Bruce is taking his time with the transition in order to give his family - which includes ex-wife Kris Jenner, daughters Kylie and Kendall Jenner and sons Brody and Brandon Jenner - time to adjust to the change.
The insider told PEOPLE: "He's being very smart about and also respectful about his transition. Instead of completely shocking everyone, his changes have been subtle, and his family has had the chance to slowly get used to his new looks and life."
The source added that "not everyone is 100 percent on board" with his decision to live as a woman, but it is clear, "everybody loves him."
Meanwhile, Bruce's stepdaughter Kim Kardashian West recently confessed that the reality TV star was the " the happiest [she's] ever seen him".
The daughter of Kris Jenner - who has sisters Khloe and Kourtney - said: "I think Bruce is very happy, the happiest I've ever seen him...He's our dad so we support him no matter what, and I think when the time is right, he'll talk about whatever he wants to talk about. I guess I'll kind of let everyone be curious and I feel like that's his journey to talk about."
The 34-year-old beauty added she is sure Bruce will speak out about his "journey" when the "time is right".
She said: "I think everyone goes through things in life, and I think that story and what Bruce is going through, I think he'll share whenever the time is right. I feel like that's his journey to talk about."