The 33-year-old television personality discussed her future with the 26-year-old NBA star in the Aug. 13 issue of You magazine.
"Tristan is a great dad and he definitely wants more children, but we both feel that it will happen when the time is right," Kardashian said of the Cleveland Cavaliers player, who shares 8-month-old son Prince with Jordan Craig.
"We're still in a new relationship and I love us having time together," she explained. "Once you have kids you can't get back your non-kid years ... You worry about your children for the rest of your life."
The Keeping Up with the Kardashians star also said she isn't in a rush to marry Thompson. She finalized her divorce from ex-husband Lamar Odom in December after initially splitting from the former NBA player in 2013.
"I'm in the best relationship I've ever been in and it doesn't take a ring for me to feel that way," the television personality said.
"I believe in marriage and I want to be married again one day but I don't have a time frame," she added. "Why do people think that marriage equates to happiness? There are a lot of people in unhealthy marriages."
Kardashian and Thompson were first linked in October following their respective splits from James Harden and Craig. The reality star said on the June 11 episode of Keeping Up that Thompson wants "five or six" kids with her.
"He wants to have kids now," Kardashian told sister Kim Kardashian.
"Tristan and I definitely talk about starting a family. He wants to have five or six kids with me and that's lovely. We could start at one and we could grow from there," she added in a confessional shot. "It's scary. It's a really big step."