He said Matt was against the idea at first but soon decided to try it and the couple met Cait.
The trio now live together in a one bedroom apartment and say their relationship is better than ever before - despite disputes about who sleeps where in the bed.
Even Matt's grandfather has welcomed the unusual relationship and often asks when they are going to adopt a child.
Cait told the Sun: "When we meet somebody at a bar I will usually say 'hi, I'm Cait and these are my two boyfriends.' People often ask if I'm joking."
Talking about the "throuple's" sex life, she said: "I had never been with two people at the same time before. It's different strokes for different folks but I would say it's a pretty fun sex life."
Chris, Cait, and Matt say the best thing about being in a throuple are the extra gifts. Photo / Facebook
Cait and Chris say they are bisexual while Matt defines himself as homoflexible, meaning he prefers men but is open to women.
He said: "I guess I had an awakening after I had a sexual experience with a woman. It is just another body, another soul, a connection that I can have."
Cait, who officiated her boyfriends' wedding, said she was jealous at first because she liked Chris more than Matt and was frustrated that she would have to share him with Matt.
Chris, 38 and Matt Brandt, 28, are in a throuple with Cait Earnest, 28. Photo / Facebook
Matt said he was also jealous of Cait because he thought Chris would love him more than her, but both said they soon came to terms with their place in the relationship.
The "throuple" say they are thinking about having children in the future and believe any child would be "lucky" to have three parents.
But Matt said they are happy with their two dogs for now.
