Kim Kardashian West's newborn son ''looks just like'' his big sister Chicago.

The 38-year-old reality star and her husband Kanye West welcomed their fourth child together, and second born via surrogate mother, on Friday (10.05.19), and Kim has now said the tot bears an uncanny resemblance to his big sister Chicago, who was the couple's third child, and first child born via surrogate when she was welcomed into the world in January 2018.

Kim - who also has North, five, and Saint, three, whom she carried and gave birth to naturally - wrote on Twitter: ''He's also Chicago's twin lol I'm sure he will change a lot but now he looks just like her (sic)''

The 'Keeping Up with the Kardashians' star was advised against getting pregnant for a third time because she'd suffered complications with both her previous pregnancies, and so has hired gestational carriers to carry both Chicago and her newborn son.

Kim announced the birth of her fourth child - whose name is not yet known - earlier on Friday, and said the tot was ''perfect''.

She tweeted: ''He's here and he's perfect!''

The tot's birth comes after Kim's sister Kourtney Kardashian revealed on 'The Ellen DeGeneres Show' on Thursday (09.05.19) that Kim's surrogate had gone into labour.

Appearing on the show alongside her mother Kris Jenner - who was unaware of the impending birth - Kourtney said: ''So, my mom doesn't even know this - but Kim's surrogate went into labour. So she's at the hospital.''

A delighted Kris screamed: ''No! What are we doing sitting here? Come on, Ellen. Fire up the car.''

Show host Ellen then added: ''So, we had to keep it quiet, but yes, that's why she's not here. Because the surrogate went into labour so she's there.''

And Kourtney said: ''Nobody knows, so everyone in the audience, don't tell.''