Well, the answer is here: Amber Rose!
Chyna's best friend has revealed she was the very first person besides the parents-to-be to learn about the pregnancy, telling People: "I wanted to shout it out to the world like this is my baby, but I couldn't. I was screaming and like 'Oh my God we're having a baby!'"
The newly-engaged couple's happy baby news was leaked at the start of May, ahead of their planned announcement on US Mother's Day.
After the news was announced, Rob said of his fiancee: " "I fell in love with her immediately because of how great of a mum she is and now I'm looking forward to starting a family with her! Thank you Chy for everything you do for me."
It will be the first child for Rob and Chyna's second, as she's already mum to son King Cairo, three, from her relationship with rapper Tyga who is now, in a twist, dating Rob's sister Kylie Jenner.
Last night, Chyna and Rob made their first public appearance together since the baby news, cuddling up on the red carpet in Los Angeles at the launch of Chyna's new ChyMoji range.
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