Correct, a "married" quad (really more like side by side triads since the men weren't involved (and I feel bad saying men, she was at the time and has now transitioned)) for 11 years with 4 kids, and a house.No, you're thinking about it just fine. You certainly have had experience with trying to do triads (and quads, I believe).
Have had several successful triads too, always walk away being better.
The only way this isn't an immediate red flag, would be if this was a master slave scenario... whats the saying. Something about not pissing on someones kink, god my brain... Its not my thing, I dont dig the whole M&S scene since it feels like a red flag from the get go. However if that is what this is, the leans a little more towards intentional nonconsent.