Kim Kardashian West and North West. Picture: Instagram

Kim Kardashian West has admitted she was pleasantly surprised by how "nice" her eldest daughter North was to her youngest Chicago.

The 'Keeping Up With the Kardashians' star has made no secret of the fact her eldest daughter North, four, struggled to adjust when her little brother Saint, two, was born because she didn't like having to share her parents' attention with someone else. 

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But the 37-year-old businesswoman has admitted she was pleasantly surprised when she introduced their third child Chicago - born via a surrogate in January - to her. 

Speaking to 'Entertainment Tonight', she said: "They love her. I'm so shocked that North is so nice and she's still... it's her world and she's the sweetest, but it's more like she and Saint have a thing. She's very warm with her sister."

The brunette beauty thought Saint would've been riddled with jealously when little Chicago entered the household, but he smothers her in "kisses and hugs" every day. 

She explained: "I was more worried about him, that he would be more jealous, [like] how North was with Saint. But he's so good with her. Every day he has to give kisses and hugs. Literally, as I was walking in, [I was looking] on my phone at the video Kanye sent me with the kids trying to climb into her crib."

Kim and her husband Kanye West, 40, were forced to hire a surrogate to carry their third child because doctors had warned the reality TV star that she may die if she were to fall pregnant again due to the complications she suffered during the first two. 

She said: "It [using a surrogate] really is a game-changer, not having to breastfeed and get back into shape. I mean, I was so proud of myself that I did that [with the first two], but I do feel like my house is so full. But in the best way. It's amazingly full."

And the showbiz couple - who have been married since 2014 - wouldn't rule out having another baby in the future but Kim doesn't know if she could handle more.

She said recently: "I've gotta live for a second. I mean, if it were up to my husband, we'd have like, seven, but, you know, it's a lot. It might change, I don't know. Maybe four is all I can handle. Maybe three is all I can handle."