Everything to Know About Bruce Jenner's Transition Before His Big Interview

In January, PEOPLE confirmed what many had been speculating for months: Bruce Jenner is transitioning from male to female.

As fans prepare to watch the Olympian speak about his journey for the first time Friday in a 20/20 interview with Diane Sawyer, here is everything we know so far about Jenner’s journey.

His Transition Has Been Gradual

Jenner, 65, made a point of slowly changing his appearance – like growing his hair longer – so his loved ones would have time to fully process his choice.

���He’s being very smart about and also respectful about his transition,” an insider told PEOPLE. “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.”

It’s Been a Secret Struggle

Jenner has been dealing with his identity for more than five decades, and his decision to come forward was not an easy one.

“He had enough of trying to fool everyone,” a source told PEOPLE. “Once he realized he was done taking a backseat in his own life, he knew it was time to be honest with himself.”

Society’s growing acceptance of transgender people was also a factor, with stars like Laverne Cox and Amazon’s series Transparent finding huge success in show business.

“He suffered from feeling a lot of shame about this for a lot of years,” the source said.

His Family Is Standing Behind Him

A source told PEOPLE that ex-wife Kris Jenner “had the most difficult time of anyone in the family” with accepting Jenner’s transition.

“She has had a lot to process. She has cried a lot about this, because it’s an emotional thing for her,” the source said, adding that she has since come around.

Meanwhile, Jenner’s children from his two previous marriages have known about the possibility for years – and sons Brandon and Brody Jenner are “fully on board,” a source told PEOPLE.

Jenner’s mother Esther is “proud” of her son, saying she’ll “always love him.”

Kanye West and Scott Disick have also embraced the change.

A source said that Kim, Khloé and Kourtney Kardashian were the last to know but are fully behind their stepdad.

“The number one thing is they all support Bruce,” a source told PEOPLE of the Kardashians and Jenners.

In fact, Kim Kardashian West told reporters that the entire family will rally around Jenner and watch Diane Sawyer’s interview together Friday.

He Has Hollywood’s Support

Boy George, Andreja Pejic and Elton John have all congratulated Jenner on coming forward.

His Relationship with Kris’ Best Friend Remains Unclear

Before his transition news went public, Jenner was spotted out and about with Ronda Kamihira, a close friend of his ex-wife. Keeping up with the Kardashians filmed fallout among his family members, who saw the relationship as a betrayal.

Whether they were dating or simply platonic is still up in the air, and Jenner has not yet addressed his sexuality.

“Who knows how intimate things got, but they knew each other for a very long time,” an insider told PEOPLE. “It seems more like he confided in her. She would buy him feminine things he wanted. They had some kind of special bond.”

He’s Happier Than Ever

“He’s so happy and excited,” a source told PEOPLE after Jenner came clean to his family. “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.”

Bruce Jenner – The Interview airs Friday at 9 p.m. ET on ABC.

For more information about transgender issues, visit the Human Rights Campaign GLAAD and PFLAG.