The couple, who tied the knot in an intimate ceremony in August, announced the exciting news to PEOPLE, opening up about the milestone in their relationship.
"We've taken another step in the adventure that is our life together," Brown told the outlet. "We didn't try, and we didn't not try. We figured that we'd just kind of let God and nature take their course and we ended up pregnant."
The couple also revealed that they already know the sex of their little one on the way, though they are planning to keep that news a secret for now. They do, however, have a name picked.
"Before we were even married, we had talked about names," Brown said. "It was one of the things that we just matched up on perfectly: We knew we wanted three children. But we didn't know what we'd get, so we set out and we picked three boy names and three girl names."
Little baby Brown will be welcomed in spring of 2019, which, as Brown pointed out, is fitting for his nature-loving family.
"Spring is when the birds have their babies, and the deer have their babies, and the bears and the cougars, so we're gonna have our baby too," he said. "We just fit right in with the animals."
The couple also revealed that their pregnancy isn't going to stop them from helping out on the homestead in rural Washington state.
"We're always working, we never stop moving up on the mountain. I've even had to tell Noah, 'Listen, if you keep picking up things for me, how am I going to stay in shape for when I need to pick up my baby?'" Rhain said. "I figure that if we just keep up what we always do, which is having a really good work ethic and working long and hard, then when the baby is born, it will grow up seeing exactly what a real family can accomplish."
Noah is already planning for the little one's nursery, revealing that he is about to start make his first child a special gift.
"I'm starting construction very soon on a cradle for the little one," he said. "I'm gonna build them their cradle and Rhain's gonna build a mobile and I'm gonna build a little baby rattle. That should be cool, I think."
The youngest of the Brown sons and Rhain met in Hoonah, Alaska in 2016 while Rhain was traveling. In April of 2017, Noah proposed to Rhain at sunset after a hike in Juneau. Now, as they embark on the next adventure in their relationship, they are continuing to receive the love and support of their families. Brown's mother Ami cried when she learned of the news, and Rhain's brothers are already being overprotective.