Caitlyn Jenner
Meet Caitlyn Jenner: Bruce Jenner's new identity debuts on the cover of Vanity Fair magazineReuters

Caitlyn Jenner's four older children have been supportive of their father's sex change, but are refusing to appear in her documentary series for E!, the same network that produces Keeping up with the Kardashians.

According to journalist Buzz Bissinger, who wrote Jenner's coming-out story for Vanity Fair, the former Olympian's children fear the series will become a "spectacle". Bissinger told reporters the four — Burt, Cassandra, Brandon and Brody — believe she could "have a legacy, really, along the lines of Muhammad Ali, an athlete who has made social change".

"That was a hard decision for them, because these are Jenner kids, trying to reconnect with their father after a long, long absence. He was, she was, desperate to have them do the show," Bissinger said during CBS's This Morning.

He continued, "And at their own risk of financial gain and exposure, they said, 'No, we are not going to do it. We do not want to participate in something that we are concerned will be a spectacle because it's being produced by the same company that did Keeping up with the Kardashians."

Children urged a rethink

Jenner's adult children even went as far as trying to convince her not to do the show. Bissinger told NBC's Today show the older Jenner children told their father, "You could be a real trailblazer here in becoming a woman, in becoming a transgender woman, don't blow it with spectacle".

The foursome, from Jenner's two previous marriages, have been very supportive of Jenner's transition, even appearing on her April interview with ABC's Diane Sawyer. Thirty-four-year-old daughter Casey revealed that the two have become incredibly close since Jenner, formally known as Bruce Jenner, introduced her female identity.

Casey Jenner said she found out at age 13 that her father had wanted to abort her and was absent from her birth. Jenner also admitted to being an absent parent to Casey and her three brothers. However, the two have gotten along since Bruce became Caitlyn. "We talked more than we ever have," Casey said. "We could just be girls together."