Originally Posted by ClosetPoly
Now, my partner has stated that her highest wish is to have a triad, to have both of us around at the same time, as a family.
Well, to have a triad, you'd have to be involved with him, too. Are you bi? If not, it's gonna be quite difficult to have a triad. As you've not mentioned being bi, then I'll guess you're hetero and your relationship is going to be a vee.
The next question is whether you want your vee to operate as a group at all times. If you don't want that going on, then it's up to you to reinforce your boundaries and let her know you don't want that.
My wife and I, for example, don't arrive as a matched set in our relationships with other people. She doesn't go along on my dates with others and I don't go on her dates with others. That's something in which I have absolutely no interest and isn't likely to happen without it being a bi lady who gets involved with each of us separately and then convinces us some group dating would be enjoyable.
So, just because your partner wants to have the three of you together because she thinks it would be wonderful doesn't mean it's going to be wonderful for you. You're the only person who can decide that, and if you don't care for the idea, don't do it.