Kim Kardashian West. Picture: YouTube Screenshot

Kim Kardashian West doesn't believe Tristan Thompson will ever stay faithful to Khloe Kardashian after hearing rumours about his antics.

The 38-year-old reality star and her famous family were stunned when photos emerged of the basketball player seemingly getting close to another woman just days before the 'Revenge Body' host gave birth to their daughter True in April, and Kim was horrified when she was then alerted to more rumours about the sportsman's behaviour.

Speaking on 'Keeping Up With the Kardashians in scenes that aired on Sunday, she said: "Honestly, I'm in shock. We love Tristan. This is honestly nothing that we suspected. We thought she finally found her Prince Charming, [her] happy ending. And then f**k. It's just, why her? It just really, really sucks.

"So many more stories are coming out. So many friends are calling me with so many more things. 

"I told her, 'What are you going to get out of him? Think about it. You're going to be worried and nervous and have an insecure life, because if he's not faithful now, he'll never change.' 

"When one thing comes out you're kind of like, well, okay, maybe the video's old or maybe it's a misunderstanding. Because a picture doesn't always tell the full story.

"But then two more stories come out. This is just crazy. Now you know it's true."

Before Khloe, 34, could make any decisions about her future, she went into labour and begged her family to remain civil towards Tristan, 27, when they arrived in Cleveland.

She said: "Everyone wants me to make a decision right this second and I just want to go and give birth and focus on that and try to enjoy this and try to enjoy it with him, as crazy as that sounds.

"I want to enjoy this with him. I don't want any negativity in the delivery room. I don't want anybody to talk about it, make me feel uncomfortable or make him feel uncomfortable. Let's just act normal. Give me a minute."

Kim - who has children North, five, Saint, two, and Chicago, 10 months, with husband Kanye West - agreed, but couldn't resist making a joke.

Miming cutting her throat, she said: "I'm going to look at him and just be like ..."

But Kourtney Kardashian - who has Mason, eight, Penelope, six, and Reign, three, with former partner Scott Disick - "respected" her sister's decision, though she admitted they were all in an "awkward" situation.

She said: "I know how important it is for Khloé to have Tristan there, and I actually really respect that.

"But it's definitely going to be awkward. It's going to be hard to even look at him or eve