Kim Kardashian West ''didn't respond well at first'' to Kylie Jenner's rumoured pregnancy.

The 20-year-old reality star is believed to be expecting her first child with her boyfriend Travis Scott, and whilst it was previously reported that her famous family are ''excited'' by the news, her half-sister Kim was less than thrilled.

Kim - who has four-year-old daughter North and 21-month-old son Saint with her husband Kanye West - is believed to be expecting her third child via a surrogate after doctors warned her against getting pregnant again, and reportedly took ''a lot of time'' to process the news of her younger sister's own pregnancy.

A source said: ''Her first reaction was, 'Seriously?' She didn't respond well at first. It's like she and Kanye had gone on this whole journey to get pregnant for months, and now this happens to Kylie. She teared up. It definitely took a lot of time for her to process it.''

But the insider insists that the 36-year-old beauty isn't jealous of her sibling, and is ''going to support Kylie 100 percent'' throughout her pregnancy.

They added: ''Of course Kim is happy for Kylie. She's going to support Kylie 100 percent, no matter what. There's never been any question about that. But it's just a weird dynamic, after all that Kim did to intentionally have another child. It has taken a lot of time, energy and money for her to get pregnant, and now Kylie is having a baby around the same time.''

And the famous family are ''genuinely happy'' that both Kylie and Kim are believed to be expecting their new arrivals at around the same time, as ''family is everything'' to them.

The source told People magazine: ''The babies will be the same age, and will probably be very close. Family is everything for the Kardashians, so they're going to focus on these new kids in the family. Everyone is genuinely happy.''