Kourtney Kardashian and Scott Disick have a long history together, much of it troubled. But emerging from the ruins of their romantic relationship, they have managed to extract a strong partnership, built on the foundation of the three children they share together. (The pair share Mason, 9, Reign, 4, and Penelope, 6).

Kardashian, 40, covers the latest issue of Paper magazine, and inside, she opens up about her surprisingly amicable relationship with not only Disick, 35, but his girlfriend, Sofia Richie, 20.

She says the trio’s friendly relationship is “probably the thing I’m most proud of.” Kardashian says the trio even vacations together with the kids. She says: “I don’t think we’ll go on every trip together, but I love that I’m invited.”

Kardashian and Disick broke up four years ago after nine tumultuous years together. Disick and Richie have been together for about a year and a half.

On a recent episode of Keeping Up With the Kardashians, Disick shared his thoughts. “She’s a better person than I am,” he added. “I thought for a very long time that I was going to live a very miserable life. I didn’t think that I was going to have happiness again. My biggest thing to Kourtney was no matter who we’re with, even though our children might not see everything, they do feel it and they can hear it and everyone needs to be okay with each other.”

Keeping Up with the Kardashians airs Sundays (9 p.m. ET) on E!