We kind of fell into ours. I knew I was Bi. My ex husband and I were swingers. Met another couple. That couple fell apart. Through a lot of bumps and rocky places.... we ended up divorced. Still friendly. Ended up dating again... and I was dating male from previous couple. That was rocky too. Ended up they were both bi. Never would I have expected that from my ex.
It took a while but we ended up in a committed triad. We already knew each others kids. And we are closeted for the most part. Everyone thinks I'm some kinda slut since we all live together. They aren't ready to come out... but we have really settled in. In fact there us going to be a legal marriage and we are considering taking on the last name of one male as a middle name for the ones getting married.
This is the happiest I think any of us have ever been. We have had a lot of ups and downs. And with each couple there is adjustments. Since I am Bi I would like to find a fourth. But I am sure finding a big female wanting to be committed to all three of us is going to be hard. But if/when we find the right one I am confident it will work out.