It can be platonic, familial, romantic, anything.
I’ll start: I recently moved in with my boyfriend, who lives with his wife and their son. They were already separated when we met, but his wife doesn’t want to divorce or move out, and she wants their son to live with both of them. My boyfriend agreed to those terms.
So now I’ve found myself in a pretty unusual situation…
That’s really unfortunate. ENM can be truly excellent, but only with the right partners and the right mindset. It takes all the difficulties of one monogamous relationship and multiplies the difficulty by a thousandfold, for sure.
Honestly I’ve always found it to be easier for me. Not to say many don’t find it more difficult, but I found monogamy to be stressful and nonmonogamy to generally just be a logistics problem rather than an emotions one.
Different people struggle with different things though
Porn hasn’t helped it either. It’s a popular topic but you only see the brief moments and not the after, and like you said, it takes both compatible people AND an agreement on expectations. One person strays from that, and you’ve messed things up for probably everyone involved with each other. I think it would only work if each person cared for the others at the same level, and not one being an “extra”.