Hello and Welcome (if I haven't said that already)!
Like Vixtoria I am a "hinge" in a MFM Vee with my husband and my boyfriend. I also am Bisexual and have a few casual female FWBs (some of which also have played with me and MrS, my husband, although this is not expected or required).
The first is how do you decide who the V is in a poly relationship? I've always wondered if this just happens or do you and your primary partner decide?
(Vixtoria already clarified the V/hinge terminology)
Some people are specifically "looking for" this relationship configuration. Lots of other Vees form when people are attempting to form a "Triad" (three people who are all involved with each other) and it turns out that two of the three are interested in one but not necessary in each other.
Personally, I have never "looked for" a relationship, I have always just "found" myself in the (few) relationships that I have been in. Relationships, for me, are things that grow and happen between two people. You are either open to the relationship and feed/water it so that it grows stronger (in whatever ways are appropriate to
THAT relationship)...or you don't, and it fades away (this applies to friendship-type relationships as well).
Two: How do you pick/find other partners? Does the primary partners date the the secondary together? Does the hinge just date and the other primary gives input in the matter?
I've never "looked for"/"picked" a partner - they fell into my life. But, that is just how I am. Many people seek partners the same way they would if they were single - meet people/get to know them/figure out if you want to date. People do this IRL and online. The added wrinkle is the full disclosure of your relationship status so that you aren't pulling a bait-and-switch where they think they are buying into a "monogamous" type set-up and then you reveal your "baggage" (i.e. that you are in other relationships).
How much input other partner's get? That is probably highly dependent on the people involved. Some people date completely autonomously - where partners know about each other but don't meet or interact. Some couples have "rules" about having to meet (and approve of?) other potential dating partners. In our situation, we expect that we will meet any other partner's at some point (and would be concerned if the other partner wasn't willing to at least MEET us) and would certainly take another partner's opinions into consideration (for instance, my husband trusts my judgement about people's motives more than his own). But the level of friendship/involvement with metamours would depend on mutual interests/budding friendship/attraction/etc.
Three: How does it work if one of the primary pair is bisexual, but the other one isn't?
Since group sex and shared partners are not a "requirement" for poly...it doesn't necessarily
have to affect anything. Some people have "rules" that allow the bisexual person to only date members of the same (or opposite) sex. MrS and I had a "rule" like this - an OPP (One-Penis-Policy) - which I didn't really understand but never really bothered me (except on an intellectual level)...until Dude came into the picture (you can read more about this in my Journey blog here if you are interested - short version: I am more likely to be attracted to women anyway, I don't like most men, BUT my most significant relationships are with men - go figure
).
Four: How do you deal with a poly relationship if they primary pair has children and then decide to open the relationship?
I'll leave others to answer this - we don't have kids (another long story). If you search the forums there have been a number of threads on this topic. (Maybe search for poly and children?)... I recall, back when I subscribed to "Loving More" magazine that there was an entire issue dedicated to the subject.
JaneQ