"Bruce is transitioning to a woman," a source close to the family told People. "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 and reality TV star's change has been a gradual one (such as growing out his hair, wearing nail polish and makeup), which the insider says is so his family could have time to adjust to the change.
"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."
In addition to children Kendall, 19, and Kylie, 17 (and step-children Kim, 34, Khloe, 30, and Kourtney, 35, and Rob, 27) with ex-wife Kris Jenner, Bruce also has 2 children with ex-wife Chrystie Crownover (Cassandra, 34, and Burt, 36), and 2 children with ex-wife Linda Thompson (Brody, 31, and Brandon, 33).
The source further shared that "The [kids'] concern seems to be Bruce's happiness, and he acts very pleased with his new life... It is an intense thing. Of course not everyone is 100 percent on board. Different people have different reactions. But everybody loves him."
He's now decided to make his journey a public one by sharing his transition in an E! docuseries, which could air as early as May.
"The family is really giving this space and time to Bruce. This is his story and they want him to tell the world the way he wants. They really want to empower him to tell his story so that hopefully he can help other people too. That's the goal."
TMZ reports that Bruce filmed his official announcement to his family last month, and that during the conversation Kris freaked out. "The other kids -- the boys and the girls -- have been more supportive, especially the older ones", TMZ notes.
Earlier this week, Bruce was also spotted being filmed by the cameras while on an outing with Khloe and Scott Disick.
He made the personal decision over a year ago, according to TMZ, when he underwent a "laryngeal shave" operation to smooth out his Adam's apple. At the time, TMZ's sources told them it's "one of the first steps". Now, Bruce is far along in the process, having undergone various procedures already as well as psychological counseling.
Finally, a leader in the transsexual community also revealed that they've known of Bruce's decision for "way more than a year".
"He has come out to those closest to him," says the family source to People. "He's so happy and excited. He gets to lay down a huge bag of bricks. He's been through a dark period and is coming out on the other side."