Cassie has shared the first picture of her newborn daughter Frankie Fine

And now, the first-time mom has posted an adorable snap of their little bundle of joy on Instagram, and gushed that she's "just different".

She wrote alongside the black and white photo of Frankie holding her hand with just part of her head on display: "She's just different. Frankie Stone Fine. My BFF."

Khloe Kardashian - who has 20-month-old daughter True with ex-partner Tristan Thompson - was one of the first to send well-wishes to Cassie.

The reality star commented on the post: "Congratulations beautiful!!!!! You're a mommy!!!!! (sic)"

Cassie revealed the couple were set to become parents back in June on Instagram.

Alongside a slideshow of images of herself and her boyfriend sitting in a car, she wrote: "Can't wait to meet our baby girl [heart emoji] Love You Always & Forever."

Alex also shared a touching letter he wrote to his unborn daughter and pledged to always be her "number one fan".

Alongside a photo of him kissing Cassie on the cheek, he wrote: "I will be the first man in your life and will show you the greatest love and affection now and forever.

"I never thought my heart could grow bigger after meeting your mother... then I found out we were having you and I instantly felt a love that is so indescribable.

"I promise to be at every dance recital, concert, sporting event, school plays whatever you decide to do I will be there and support you. I am your number one fan.

"I promise to be a man that you and your mother look up to and love. I will always listen and put the both of you first."

Meanwhile, the 'Me & U' hitmaker - who previously romanced P. Diddy - recently admitted she was "a little scared" of giving birth, because she didn't know what to expect from the labour process.

She said: "I am feeling great, but I'm a little scared of labour. I keep reminding myself that our bodies are meant to do this, and in the grand scheme of things, it will be over in a blink of an eye. In general, I keep hearing that parenthood goes by fast, so I'm trying to make every effort to enjoy each moment and all the stages, no matter how uncomfortable."