Rob Kardashian was baffled and asked "who is this woman" when he saw Caitlyn Jenner for the first time.

Rob Kardashian

Rob Kardashian

The 28-year-old TV star had no idea Caitlyn was his former stepfather Bruce Jenner - who is now living under the new female identity after undergoing gender transition treatment - when his older sister Kim Kardashian West, 34, sent him a photo of her.

Kim - who has just announced she is pregnant with her second child with her husband Kanye West - revealed to 'Access Hollywood Live' that Rob was completely unaware Caitlyn was doing the Vanity Faire shoot and so he replied: "Kim, why are you sending me this? Who is this woman and why do I care? And I was like, Rob, that's Bruce - that's Caitlyn. And he was like, "Oh my god, she's beautiful.' "

She also said: "I've been on the phone maybe five different times sending it to all the family members ... So I sent it on a mass text to everybody ... It was so funny because all the girls, we knew Caitlyn was shooting this, but my brother had no idea."

Rob - who has kept quiet about the emergence of Caitlyn on social media - immediately called Caitlyn to congratulate her and they had a "love fest".

Kim was on hand to aid Caitlyn with her Vanity Fair cover shoot and was thrilled that they even share similar hair styles.

Kim also offered Caitlyn sound advice for modelling in front of the camera.

She said: "Just practice, practice, by yourself until you feel comfortable."

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