Caitlyn Jenner admits she hasn't been the 'perfect' stepparent to the Kardashians

Caitlyn Jenner has admitted she hasn't been the "perfect" stepparent to the Kardashians.

The television personality made the admission as she celebrated her stepdaughter Khloé Kardashian's birthday on Tuesday by posting a photo of the pair together during Khloé's 2009 wedding to her now ex-husband Lamar Odom.

"Happy birthday," Caitlyn wrote in the Instagram caption. "Being your stepfather was, and is, one of the best things that I was ever blessed with by your mother. I promised your father that I would do my best to always be there for you kids and I know I haven't been perfect but I will always love you and you are forever in my heart."

She concluded, "I hope your day is filled with love, your kids, and happiness."

Caitlyn married Kris Jenner in 1991, becoming a stepparent to the Kardashian children Khloé, Kourtney, Kim and Rob Jr.

Before Caitlyn, Kris was married to Robert Kardashian from 1978 to 1991.

The television personality publicly came out as transgender in April 2015, one month after her divorce from Kris was finalised. Caitlyn and Kris share two biological children together: Kendall and Kylie.