Kim, Khloé and Kourtney Were the 'Last Ones Let In' on Bruce's Transition: Source

The Olympian's three stepdaughters learned the news after other family members were told, a Kardashian insider tells PEOPLE

Photo: JB Lacroix/WireImage; Inset:Ethan Miller/Getty

His lifelong secret now out in the open, Bruce Jenner faces different reactions to his transition from his famous family. Subscribe now for instant access to all the details on the divided Kardashians and Jenners, only in PEOPLE.

Bruce Jenner has long enjoyed a close relationship with his three stepdaughters from his 23-year marriage to reality-TV matriarch Kris.

But lately that relationship has been tested as the gap widens between the Jenner and Kardashian families.

In recent months, Jenner’s transgender journey has made headlines around the world – and although they are supportive, his stepdaughters have also struggled with the news.

Kourtney, 35, Kim, 34, and Khloé, 30, “were the last ones let in on it all,” a Kardashian insider tells PEOPLE in this week’s cover story.

That’s in contrast to Jenner’s children from his previous marriages – Burt, 36, Cassandra, 34, Brandon, 33, and Brody, 31 – who had known about the possibility of their dad’s transition “for years,” says a source close to them.

As for the two daughters he shares with Kris – Kendall, 19, and Kylie, 17 – “they are having a hard time with the transition,” adds the family insider. “They’re very supportive, but it’s just not an easy situation.”

• Reporting by JENNIFER GARCIA

For much more on how Bruce’s family is handling his transgender journey, pick up this week’s issue of PEOPLE, on newsstands Friday

Behind PEOPLE’s Cover: Bruce Jenner’s Family Divided