Kourtney, 30 – who's since reconciled with Disick, 26 – told her sister Khloe, 25, first. The outspoken younger sister, one-half of the new E! show Kourtney & Khloe Take Miami, was then put in charge of disseminating the news to sister Kim and mom Kris Jenner.
"It was so hard for me to tell Kim and my mom," Kourtney tells PEOPLE. "Khloe and I called Kim on speakerphone, and I made Khloe tell her. I think Kim thought we were lying! Kim was excited, but I feel like her first reaction was like, 'Why? What are you doing?' It was really just shock. Especially since we are so extremely close, anything that happens in our family is earth-shattering to us. But she was excited. She just wanted to make sure that I had thought this through."
Telling MomKourtney waited until she returned home to Los Angeles to break the news to her mom, Kris. "I was scared," Kourtney admits.
So with Khloe at her side, Kourtney says she told Kris, "Okay, we have to tell you something. It's serious." Khloe then broke the news to Jenner, whose initial reaction was a mix of shock and joy. "It took her a minute to digest it," says Kourtney. "She didn't even know Scott was around since we broken up, so was like 'Scott, who?' "
Since then, though, Kourtney says her mom and Disick get along, and any issues they had are a thing of the past.
Next up, was to tell her half-sisters, Kendall, 13, and Kylie, 12, who's dad is Bruce Jenner. "They were like the only people I actually told myself," Kourtney says. "I took them out for ice cream, and I said, 'You guys, this is so weird. Don't get freaked out, but I have to tell you something.' They were so excited. Kylie calls me 'fatty' every time she sees me, like 'hey, fatty!' "