The 42-year-old reality TV star was criticised for suggesting that her sibling get pregnant via IVF with Scott, despite the pair having both moved on with other people.
The pair was in an on-off relationship from 2006 to 2015.
The former couple share three children together — Mason, 13, Penelope, 10, and Reign, eight.
In the resurfaced clip from Keeping up with the Kardashians, the SKIMS founder told former pal Larsa Pippen that Disick, 39, called her to say he wanted to have another baby with Kourtney, 43.
Kardashian said: "I mean it’s like, Scott has a girlfriend, Kourtney has a boyfriend, we get it so they don’t even have to have sex. It could be like IVF."
Her pal agreed, saying: "Totally, it’s just so much easier to have the same dad."
Kardashian then said: "I have to tell the rest of the family, be like, guys should we encourage this? Like how cute will that be."
The clip was shared this week on Reddit, eliciting several comments hitting out at the star’s behaviour.
One person wrote: "Kim was only so desperate for them to stay together and have another baby because she wanted to keep her sister on lockdown and have her continue to live the boring mum life.
"I genuinely think Kim’s crazy level of jealousy gives her real fear of seeing Kourtney happy and having fun."
Another said: "Kim’s creepy, conniving smile is the one she wears when she plots.
"How dare Kourtney live a happier and care-free life than Kim. That’s not allowed!"
"What does this obsession with having the same dad for all their kids say to Kylie and Kendall, who have a different dad. That’s what I always wonder," a third commented.
Kardashian’s plot ultimately failed, as her sister married rocker Travis Barker last year. The pair tried to have their own child together through a gruelling IVF process, which has been unsuccessful.