El Moussa, 38, revealed on "GMA3: Strahan, Sara and Keke" on Tuesday that he didn't give Anstead, 36, a courtesy warning before bringing Young, 31, to Anstead's home.
“I was like, ‘Oh, I’m coming over to see the kids. By the way, my girlfriend is coming. See you in five!’” the "Flip or Flop" star recalled.
As it turns out, he didn't give Young a warning, either, that she was about to meet the "Christina on the Coast" star.
“That’s literally how it went down. I looked at Heather, and I was like, ‘Are you ready?’ And she was like, ‘Ready for what?’ I was like, ‘Well, we’re going to go see the kids, and my ex-wife is there,’" he said. "And she goes, ‘What do you mean?’ And I’m like, ‘No. We’re going right now.’ She’s like, ‘Right now. Right now?’ I was like, ‘Right now. Right now.’ So that’s how they met.”
Thankfully, the blond bombshells got along great — and to hear El Moussa describe it, he may have a type.
“They both eat that healthy, hippie food. That weird juice. They do that weird hiking stuff," he said. "You know, that weird stuff.”
El Moussa and Anstead separated in May 2016. Their divorce was finalized in August 2017. Anstead married British TV personality Ant Anstead in December 2018; the pair are expecting their first child together this week.
Christina and El Moussa share daughter Taylor, 8, and son Brayden, 3.
El Moussa and Christina still film "Flip or Flop" together despite the split, which was contentious at first.
"We're divorced and we were very curious to see what the viewers would think and it turns out they loved the show because the ratings are really really good," El Moussa told Fox News.
"I think that we're just showing the world that you can make anything happen when you want something to happen and filming with my ex-wife is a lot better today than it has been in many many years," he admitted. "It's very exciting to know that we can show up on set, do our job, and things are good."
El Moussa and Young have been dating for a few months. He recently told Fox News that he asked her out "a while back" but she had a boyfriend at the time.
When he ran into her again, she was single and accepted his second invitation. "It's early in the relationship and we're having a blast," he gushed. She's just amazing and adorable and I'm just enjoying every second."
Fox News' Jessica Napoli contributed to this report.