I was the one that initially proposed to my wife that we be non-monogamous, on our first date 4.5+ years ago. She initially wasn't interested, but was willing to try and find out what she'd be comfortable with. Over the next 3+ years she (Ginko on here) helped build a polyamorous network of friends, listened to Dan Savage and Polyamory Weekly podcasts, and read much of the materials I introduced her to, along with setting guidelines with me on what we were each comfortable with over time. She was excellent and very supportive, while I at times was impatient and not very good at showing my appreciation for all the effort she was putting into becoming ok with something that was not in line with what she'd grown up wanting. She loved the idea of monogamy, two people focused on each other and their family.
Confusion came up due in part to my lack of proper terminology. I mistakenly used polyamory as an umbrella term, while I'd just been asking for the ability to be more physically affectionate with friends as I had been when single in college, soft swinging, not even going to the point of sex, and she'd said she could potentially become ok with that but not the prospect of developing other romantic relationships. Then after a while a poly male friend, J, began pursuing her, and every step of the way Ginko and the friend were great in asking me what I was ok with. Given that we'd always just focused on what could be done physically, and Ginko had said romantic relationships would never be up for discussion, it didn't enter my mind that I was being asked if I'd be ok with them becoming romantic, while I was totally fine with them doing whatever they wanted physically as long as they were safe, which I knew they would be given their temperaments, so I simply said to do whatever she'd be ok with me doing. She begged for specific rules so that she could feel secure that she wasn't going too far but I didn't know what to say beyond that.
I was so happy that she was seeing that being physical with someone else didn't hurt her feelings with me. Then she informed me he'd asked her to be his girlfriend and she'd said yes. She thought I'd been supportive of them dating, while I thought she'd been clear that wasn't an option, so I had never really addressed it. Still, I was so happy with the rapid change in her feelings about what could be ok that I wanted to see if I could adapt, given that she'd put in so much effort to adapt for me. She'd always asked me what the benefit to what I wanted would be for her. In her experience the answer came in dating someone else, while for me if I'd known that'd be the necessary change, I'd have preferred to stay monogamous and limit affection with others to hugs. The transition from monogamy to our current status has probably been the center of ~95+% of our arguments, so if either us had known how it'd go we wouldn't have tried, but now that we're here it's more manageable, if not yet ideal.
For brainstorming, part of my problem has been that when J is around he kind of takes over Ginko's attention, at least in my perception, and he likes to drop in for a day or two at a time (often at a moment's notice) whenever he can, leaving me suddenly feeling like I've lost my weekend with her. He doesn't do planning well, but this past weekend we managed to make it work a bit better with me guiding when she saw him to some degree (I know that sounds controlling, but everyone actually seemed happy with the result), and this upcoming weekend we're going to try visiting him Friday night through Sunday mid afternoon, but often be in a separate room doing our own thing like when we're home, as he thinks he'd be happy simply to have her around even if they're not focusing on each other, as he works from home. They'll have Friday night through Saturday afternoon to themselves as I'll be working and then sleeping at home, then I'll join them and have a bit more time of my own with her, and she and I will sleep Saturday night in a spare bedroom. It's an experiment to see if we can feel more at home at his place, which would let us enjoy being there more often.