"I never even 'came out' because it was never this expectation that I was straight until I was gay," he added.
The fashionista came out publicly in Cosmopolitan's Pride Issue in March, Daily Mail Australia reports.
But despite the support of his nearest and dearest, Christian admitted it's taken "a while to really celebrate [his] own sexual identity".
Today Show host Richard has been vocal about his support of his son.
Following the passing of the same-sex marriage bill last year, he said: "My son Christian has been a passionate advocate for marriage equality.
“To see the joy and relief on his face yesterday made me very happy and extremely proud of my beautiful boy.
“It feels to me like we all grew up a little bit yesterday. I love you very much darling, very proud. Thank you.”