Welcome everyone. It's nice to have a working computer again to visit this forum with.
As for the jealousy issues it really depends on each person or situation. By that I mean are you the one that's jealous or is it one of your partners? Are you jealous of their time together apart from you or are they accidentally leaving you out? Is their connection/NRE (new relationship energy) stronger than what they feel for you?
Been there done all that and still fighting with a bit of the feeling left out part.
I'm in a triad consisting of me, my husband and our girlfriend. I'm still struggling with her passion for him that was so strong from the start and her slow to form feelings for me. I was very jealous of her passion for him and felt like a third wheel the first time we were all together.
I am very happy to say that we are all happy with being a triad and as with any relationship it takes work to keep it going and open and honest communication is what helped us a lot. When we talk we talk about everything from feelings, health, family to hobbies, theories and the weather. No subject is off limits but not all subjects interest all of us. So we don't have to all be present to talk about hobbies that we aren't all in to but we all try to be present to talk about relationship issues.
So that is my two cents on the subject. Feel free to ask any questions.