Caitlyn Jenner and Kylie Jenner. Picture: Instagram

Caitlyn Jenner has posted a sweet tribute to Kylie Jenner and her newborn daughter after the 'Keeping Up With The Kardashians' star welcomed her first child into the world on Thursday.

The 'I Am Cait' star - who was known as Bruce Jenner before undergoing a gender translation - wrote a sweet message of support for her 20-year-old daughter after she welcomed a baby into the world on Thursday.

READ: Kylie Jenner's 'more mature' since becoming a mom

Alongside a picture of Kylie herself as a baby, she wrote on Instagram:

Meanwhile, soon after the birth, Kylie's mother Kris took to social media to reveal she feels "blessed beyond belief" after Kylie welcomed her first child.

Sharing a link to the video Kylie dedicated to her daughter, Kris wrote on Twitter: "God is SO good!! I am so excited and thrilled to welcome another precious baby girl to our beautiful, ever growing family. We are blessed beyond belief! (sic)"

The brunette beauty had taken to Instagram to announce the arrival of her baby girl, who she has with her partner Travis Scott.

In the accompanying post, she wrote: "I'm sorry for keeping you in the dark through all the assumptions. I understand you're used to me bringing you along on all my journeys. My pregnancy was one I chose not to do in front of the world.

"I knew for myself I needed to prepare for this role of a lifetime in the most positive, stress free and health way I knew how. There was no gotcha moment, no big paid reveal I had planned. I knew my baby would feel every stress and every emotion so I chose to do it this way for my little life and our happiness."