Chris and Matt were a happy couple. Then they invited Cait to join their relationship.

People: if you haven’t heard the term ‘throuple’ before, then strap on your figurative seatbelts on and get ready to learn.

It seemed like your ordinary love story.

Matt met Chris. Matt and Chris fell in love. Matt and Chris put a ring on it and became Mr and Mr Brandt.

They were living together, married for six years, and the rest could have been history.

Until Chris suggested they add another person to their monogamous relationship. And it wasn’t a man.

Instead, it was Cait, a 28-year-old woman who had just come out of a serious, five-year relationship with another man.

Introducing: the throuple.

L-R: Matt, Cait and Chris. Image via Barcroft TV.

Prior to their throuple-ness (no, it's not a word, but let's go with it), only Chris had been sexually intimate with a woman.

"At first Matt was completely opposed to the idea but after a while, we talked about it and he warmed up to it," Chris told Barcroft TV.

While Chris and Cait found the relationship easy to adjust to, both identifying as bisexual, it took longer for Matt to be secure with a woman.

"I’m homoflexible so I like guys and I’m open, flexible to women - I prefer men," 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."

Listen: Madison Missina explains monogamish to Carla. (Post continues after audio...)

Now, in case you're wondering exactly what I was thinking, yes - they get jealous.

Cait admitted she found it hard to split her time with Matt because she was so much more connected to Chris.

Matt definitely felt the same, after Chris told him he loved Cait equally.

"It was a struggle, even for me. The insecure part of me was like, 'Oh, well Chris loves me more since he's been with me longer," he said.

"But, then, he told me, 'I love you just as much as I love Cait'. And, I had to come to terms with that."

The three have been living together since 2015, and are considering having children together.

Talk about modern families, right?