While the babies are due in "early November," Bass, 42, said he "need[s] them to be Halloween babies."
"They have no choice but to love Halloween because I'm obsessed and they're going to be obsessed," he explained.
Bass and Turchin, 34, first announced the news in a TikTok video on Tuesday. In the clip, which was in the style of a horror movie trailer, the pair are haunted by a "presence," hearing baby cries and giggles throughout their house. At the end of the video, the two can be seen encountering something inside their oven -- and they appeared to love what they found.
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"Coming this fall," Bass captioned the video, adding the hashtags. #TheyreComing #HappyPride #ForYourPride #TodayIsLove #Zaddies. Bass also commented, "#DirtyPops," undoubtedly a reference to the NSYNC song, "Dirty Pop."
"I love Halloween," Bass told PEOPLE. "When I found out that they were going to be coming at Halloween, I immediately thought, 'Our baby announcement has to be some kind of Halloween theme. Maybe we should do a movie trailer, a horror movie trailer where we don't actually say it. You have to figure it out.'" And so that's what we did."
"And so we called my friend, Colton Tran, who is an incredible horror director," Bass added. "We did it within three days. We had it written and everything, we shot it one day and edited it another day and it was ready. So I was so happy with how it came out. Michael has to be on board with all my crazy ideas."
Bass and Turchin also opened up about the exciting news and shared details about their years-long surrogacy journey.
"You have your vision of how it's all going to go, right? When we went into IVF and surrogacy, we had no idea what it was all about," Bass told PEOPLE. "Pretty much everyone we've known had bad luck at the beginning. The first time they tried it, it just did not work. And I feel like that is such a common thing. And it's great that we're able to talk about this because a lot of times I would believe that couples feel very alone in that situation. But to know that other people are going through the same exact thing, it's really comforting."
"We went through nine different egg donors, which is rare," Turchin added. "We picked a donor for some of them. We got all the way down the path of about to retrieve their eggs. Some just wouldn't produce enough eggs, some weren't good genetic matches. If you're going to be a match, you don't want to even risk it."
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Last March, Bass and Turchin's surrogate miscarried while she was pregnant with twins.
"It's very disappointing when that dream gets popped," Bass said and Turchin noted that they had to "start all over from scratch again this past year."
Fortunately, the two found the right surrogate as well as an egg donor who was a good fit. However, Bass said they were initially "very cautious to get excited" after they learned the surrogate was pregnant.
"It kind of sucks because when you find out you're pregnant, you want to celebrate with your family," he explained. "You start planning their future in your head already, but we were so scared because we didn't want to go through the pain again of losing them. We told our friends and family about the ninth week, when we finally felt comfortable. You think you're going to jinx it or something."
Bass and Turchin went on to share their thoughts on having both a boy and a girl.
"We always knew we wanted at least two kids, it would be nice to have a boy and a girl just to feel the experiences of raising both or whatever they end up being," Bass said. "I think it's just amazing that science has gotten this far where we can make the healthiest human beings ever. And I hope in our lifetime, we'll be able to see the whole world be able to do this."
Turchin added, "Yeah. And hopefully this'll become more affordable. Because especially with so many gay families, they end up spending so much of their money, all their savings, for that one try and it doesn't work. It's like, 'Well, what do we do now?' So hopefully it moves in that direction where it becomes attainable for everyone."
The couple -- who have been married since 2014 -- said they plan on "splitting their time" between Los Angeles and Miami.