The pro dancers have decided to take their relationship to the next level.
Hough shared a romantic picture of the two embracing with her legs wrapped around his. The post reads "engaged." The couple has been on vacation in Monaco.
"It’s only the beginning…the beginning of forever ♥️," he captioned the stunning picture.
His younger sister, 33-year-old Julianne Hough, reacted to the good news in an Instagram Story.
"Congratulations to this spectacular couple!," she wrote. "I'm so happy for you two and this beautiful life you have already started to create. This truly is just the beginning."
Hough, 37, and Erbert, 27, have been dating since 2015. Back in 2018, Hough gushed about Erbert to ET and, at the time, said he didn't feel any rush to get married.
"She's really grounded," he said of Erbert. "She's really, really grounded -- just really down to earth, and just [has] a good heart and a beautiful soul."
"Do I feel pressured getting married? No, you know what, I don't, actually," he also shared. "I'm building a house right now. I feel like I've been building it for 25 years now. It's taken a long time, so for me, I'm looking at things in stages, and for me, that's going to be the next stage. So, I can get settled, physically grounded, physically settled. And then who knows where life takes us."
ET also spoke with Hough about quarantining with Erbert, and he said their relationship had only gotten stronger. He said she was "absolutely" the love of his life.
"By the way, I don't believe any couple had ever spent that much time with each other consistently, it's so unusual," he said. "So, the fact that it's made our relationship stronger is great. We started a YouTube channel, we cook together, we do arts and crafts and things, and it is always a good sign when you are very content to sit with someone on the couch and fall asleep with four animals next to you and be like, 'This is great, I like this.'"