Florida Georgia Line's Tyler Hubbard on Keeping Thomas Rhett's Baby Secret: 'It Was Challenging But Fun'

Tyler Hubbard and Thomas Rhett are current best friends, but they almost had matching little future best friends.

During a trip to Africa, Thomas Rhett decided to hit up the gym while wife Lauren hung back at the lodge with Hubbard and his wife Hayley — a special moment he sure should have stuck around for.

“We were in Tanzania on a seven-day safari with Tyler and his wife, Hayley. And I was literally the last person to find out in our group!” Thomas Rhett, 26, tells PEOPLE.

“We were in the middle of the Serengeti and Lauren was feeling sick, and I was like, ‘Maybe you should get a pregnancy test?’ And she was like, ‘Where am I going to find a pregnancy test in the middle of the wilderness?’ ”

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“I was 100 percent sure I was not pregnant – because we were well into the adoption process at this point and we were both like, ‘Let’s wait, let’s give this adopted child his or her time with us and then we’ll continue our family,” Lauren adds. “So I was convinced it was food poisoning.”

But it turns out Lauren wasn’t the only one with baby fever. Hayley felt the urge to take a pregnancy test, too. However, while it turned out Hayley’s was negative, Lauren’s turned up positive.

“Both of our wives actually took a pregnancy test and I yelled to Lauren that we were pregnant — joking because we weren’t pregnant — and she said, ‘Yes, we are, too!’ ” the “May We All”singer, 30, says about the joke that made Lauren instantaneously reveal the results.

“I realized, ‘Oh my gosh, Lauren, I was just kidding,’ so we all celebrated — Lauren, Hayley and I really quickly — and then we ran to the gym to tell Thomas Rhett,” he adds.

Little did Thomas Rhett know the news he was about to get was a workout in itself, filled with jumping for joy.

“I wasn’t trying to be insensitive to my husband by doing the test without him — I was so sure I wasn’t pregnant,” Lauren explains. “When you’re there, you are supposed to keep a buddy with you at all times because you are in the wild. So me and Hayley were together and I was sure I was not pregnant.”

“When I found out I was pregnant, I was like, ‘Oh my gosh!’ ” she continues. “Tyler hears me and screams my name and was like, ‘Lauren, are you having a baby?’ And [I] blurted out, ‘I’m pregnant!‘ ”

“I’m jumping up and down, he’s giving me a bear hug, and Hayley’s running out of their room and I’m like, ‘Thomas Rhett is not even here!’ And [he was] on the treadmill so I was like, ‘Guess what? We’re having a baby!‘ ”

“I went to the gym and I was running on the treadmill, and the next thing I know, Lauren, Tyler and Hayley walk in the gym and they were like, ‘You’re gonna be a dad!’ ” Thomas Rhett recalls. “And I was like, ‘Tyler, how do you know that?’ ”

“It was an awesome way to find out and we couldn’t be more happy for them,” says Hubbard. “Also, we got the time to get to celebrate together, but then having to come back home and not tell anybody was challenging, but kind of fun. Definitely a cool moment we’ll never forget.”

Lauren and Thomas Rhett announced Wednesday that they’re expecting a baby — and adopting a child from Africa.

“I was in complete and utter shock. My first thought was, ‘Oh my gosh, we’re about to have two children under the age of two,’ ” the dad-to-be, whose baby on the way is a little girl, told PEOPLE of the news.

“No one is ever prepared for something like that. It is almost like we suddenly had twins.”

It was the sweetest surprise they could imagine. With not one but two babies on the way, “We feel more than blessed,” says Lauren.