Having read your other posts, I would say "Vee" - which is how I describe our MFM situation. My boys are best friends (and were before I got "involved") but not sexually involved with each other. When we are sexual all-together (which is a rare, but exciting, occurrence) their sexual attention is focused on me (as they are both straight).
I have seen others here describe an "emotional triad, sexual vee" - we are close to that, but I don't try to define the guy's relationship - that is their domain. If the term "sister-wives" didn't carry such a hefty weight then I would describe them as "brother-husbands"...
Me: poly bi female, in an "open-but-not-looking" Vee-plus with -
MrS: hetero polyflexible male, live-in husband (23+ yrs)
Dude: hetero poly male, live-in boyfriend (4+ yrs) and MrS's best friend
Lotus: poly bi married female, "it's complicated" relationships with Dude/JaneQ/MrS (1+ years)
+ "others" = FBs, FWBs, lover-friends, platonic G/BFs, boytoys, etc.
My poly blogs here:
The Journey of JaneQSmythe
The Notebook of JaneQSmythe