Caitlyn Jenner Celebrates 'First Birthday'

The "I Am Cait" star turns 66 today.

— -- Caitlyn Jenner is celebrating her "first birthday" today.

Jenner turns 66 years old today, but according to People, the "I Am Cait" star began her birthday celebrations early by having a birthday lunch with daughter Kylie Jenner, and former step-daughters Kim Kardashian and Kourtney Kardashian.

"Technically it is my 'first' birthday, and I got to share it with a couple of my daughters today," Jenner said Tuesday at Logo TV's "Beautiful As I Want To Be" web series launch party in Los Angeles. "We had a wonderful lunch. But, certainly, since coming out, this is my first birthday."

Caitlyn's youngest daughter, Kylie, posted a photo from the birthday lunch, wishing Jenner a "happy birthday" and congratulating the former Olympian on an "amazing" year.

"Early birthday lunch with @caitlynjenner Happy birthday dad what an amazing year for you," the 18-year-old captioned the photo.

Kim Kardashian-West also posted a photo from the birthday lunch, and revealed that the Jenners and Kardashians debated how old Caitlyn actually was.

"Happy Birthday Caitlyn! Are you 66 or is Caitlyn 1? lol That was the debate at our bday lunch yesterday!" wrote Kardashian-West. "Have the best day ever filled with lots of love & laughs! You have shown me what it's truly like to live an authentic life without caring what the world would think! I love you!"