I'm the hinge in a V. My boyfriend is monogamous. My husband doesn't really know. He's tried dating-but is currently not.
Of the women my husband dated, one was an AWESOME metamour, one was a f*** self-centered jerk.
The one who was awesome lasted 2 years before moving to another state.
She made a point of contacting me directly. She didn't use Maca as the go-between. This made ME feel respected and cared for by her. (to clarify she and I were not romantically or sexually involved).
She would drop me a text to find out if a specific date was booked up already with something else (like a kids piano recital, my date night or whatever). It was AWESOME for me to be able to pencil into the family calendar when she called-instead of having to deal with rescheduled events.
She invited the family over for activities that weren't "romantic" for them as a couple.
She had an "open door policy" regarding her home that was granted to ALL of us-not just Maca, but myself, GG and the kids too. Whilst we didn't go running over all of the time-it was nice to know that if we needed to talk to HER or whatever-that was ok.
She took time to find out our anniversary, my birthday, the kids birthdays, GG's birthday and my anniversary with GG. That allowed her to keep those dates in the back of her mind and not schedule things that would conflict.
She didn't talk trash. If he went to her in a moment of heated frustration with me, she would listen, but she didn't assume every word was god-given truth. She recognized that THEY had disagreements and misunderstandings and accepted that we do as well. She would express her empathy and love for him but also suggest that "it sounds like you two need to talk it out." Never rising to the occasion or taking advantage of the opportunity to disparage me.
Likewise, she was that way with me if I went to her with some frustration about him. She was excellent at accepting that what people say in the heat of frustration isn't a good reference for the full scope of a situation OR even representative of their overall emotions towards one another OR a good representation of the health of their overall relationship. It's just a circumstance and like weather-they pass.
She asked me herself, how I felt about her involvement in our life, in our family, in our home-before taking the steps he offered. Not that she distrusted him telling her she was invited or welcomed. She simply wanted ME to know that she respected that this wasn't JUST HIS LIFE, JUST HIS HOME, JUST HIS FAMILY. It is ours and therefore, she checked with all of us. She even asked GG to be sure HE was ok with her joining activities with all of us.
Basically, in addition to having respect for the rest of us as important people in Maca's life-she ensured he KNEW she had that respect. She expressed it, not vaguely, but pointedly and purposefully.
That makes a good metamour.