Special thanks to B for sharing this with me and the others on the list.
I've been there, in different ways.
The key to "meeting the needs" of the third (or really any) person is
that it depends on what the needs are. Not everyone is in a place
where they want to get married, have a long term committed
relationship, or have short term relations, or or or...
So what needs are being talked about to begin with? In the non-poly
world, the assumption is that you have a monogamous relationship and
that (eventually) one of these results in marriage. Underneath that
is a common belief that relationships that aren't aimed towards
marriage are pointless or weird or a waste of time (this is mainly a
southern thing, I didn't get as much of this in DC).
And this is a mistake that leads to a lot of strife out there: people
assume an all-fitting box that is "a relationship" when really all
people and all relationships are different and everyone needs
different things, no matter how subtle the differences are.
By pretending everyone needs the same thing or things, there are LOTS
of problems in 'typical' relationships.
So, have I been the 'third party' and gotten my needs met? yes.
The advice I would give is the same as for anyone dating anyone in any
circumstance: know theyself, and understand the person you want to be
in a relationship as well.
What do they want to give, open to give, like to give? What do you
have to give? What needs does everyone have? Does it fit?
If the answer is no then the relationship will have issues. If the
answer is yes the relationship will work until those needs change. I
was in an open relationship for a while that worked until the girl I
was seeing became clear that what she needed was something more
permanent (marriage). We had long ago discussed that I wasn't in a
place where I wanted to get married (to anyone). We broke up (but
kept seeing each other) until she found someone who fit her needs
including the new one. Then we stopped seeing each other (the other
person wasn't poly). We DID remain friends and eventually her (now)
husband realized that I was cool and not some jealous boyfriend guy.
I was happy for her because I wanted her to be happy, and our needs
and ability to give no longer matched up. This was just fine by me.
The only way any relationship works (no matter the number of people
involved) is through good communication. The more people, the more
communication usually needed. And you can only communicate your needs
if you know them. Most people actually don't. And so you have to
work hard at knowing yourself and harder at reading people and their
needs and most of all learn the skills to deal with less than perfect
communications and the misunderstandings that ensue.
There are a lot more "open relationship" people than people who
directly identify as "poly". That's a whole different can of worms
really. Many times when people hear poly they think "open
relationship" and that causes some misunderstandings from the start.
I really appreciated these comments, particularly the part about most people not really knowing what they want in the first place. I know that I have a wide spectrum of things that would fit the definition of "what I want" in a relationship, because my needs are broad enough in some ways to allow for multiple expressions of love to meet them. But I do see quite a few people who haven't given a lot of thought to or clarified for themselves what their needs are, so they either A) adopt a set of socially and culturally normative "needs" as their own without much reflection to whether or not it's a good match for them at any given time in their lives, or B) decide that socially and culturally normative "needs" are bogus and blow them off without honestly reflecting on what a set of replacement "needs" that might fill that void in a positive way would look like.
This, I believe, is at least partially the reason for many of the "OMG POLYAMORY that is so WEEEEEEIIIIRRRRRDDD" responses I sometimes get, even from people who cheat on their partners regularly and have lovers on the side. I've gotten that reaction from people who would otherwise be cool with dating a married person as long as it were done in secret (as if that is somehow a more acceptable way of going about it).
I remember what went through my mind the first time someone I knew came out to me as polyamorous and explained it as a lifestyle. My thoughts were something along this line: "HO-LEE CRAP, that is some weird stuff. More power to ya if it's working for you, but I can't imagine ever doing that myself." Luckily, the first person who ever mentioned polyamory to me was a gay man who was interested in having a purely intellectual discussion with me about it (and not someone who was hitting on me, which might have been even harder for me to wrap my head around). Without the pressure of an impending potential relationship, I was able to go home, think about it, chat about it with my partner, and within a year we were (at least mentally) on board with it. About the time we were ready to give it a shot, we ended up moving to a very, VERY conservative town and nothing came of it for years (until we relocated again, this time to a very progressive area). But I think my initial response to hearing about poly wasn't MY response-- it was a socially conditioned response that I had accepted as a norm without any reflection. A little reflection later, and here we are, moving into poly ourselves.
At any rate, I appreciate the first-hand reflection and advice from someone who has been a "tertiary" partner to someone already in a committed relationship.
Interestingly, my request for experiences from those in a tertiary relationship to share their thoughts with me has led to an off-list email and continuing discussion from and with someone who is currently in a relationship with a person in a committed relationship, who had been quietly going through her own anxieties about whether or not the other partner could truly care about her experience, feelings, and needs. What a refreshing connection to make and conversation to have, even if it isn't MY metamour, and I'm not hers. The universe has truly blessed me with good people at the right times. I have not reason to doubt that would continue.