Kelly Osbourne is "so proud" to be Sharon Osbourne's daughter.

Kelly and Sharon Osbourne

Kelly and Sharon Osbourne

The 30-year-old star has penned a touching tribute to her mother in a new book, 'A Letter to My Mom,' by Lisa Erspamer, but admitted she used to be afraid of "becoming just like" 'The Talk' co-host, 62.

She wrote: "As a teen and up into my mid-twenties, I did everything I possibly could to make myself different, not only to my detriment but to yours as well... Like all teenage girls I had this ridiculous fear of growing up and becoming just like you. I was so ignorant and adamant about creating my 'own' identity."

But the former 'Fashion Police' star eventually realised that she and Sharon are very similar.

She explained: "I woke up one day and realised that I am you. How could I not be? Why had I been fighting the inevitable for so long?"

Kelly then gushed about Sharon, who previously battled breast cancer, and praised her for being the "strongest person" she has ever met.

She said: "You are the most beautiful, kind, generous, loving, and -- let's not forget -- strongest person I have ever met and the best part is that you are MY mum. I am so proud to be your daughter."