I'm a cis-man in a long term committed polycule with a man and a woman (10+ years). I don't know enough about the lifestyle to explain what we are but predominately he and I are a couple, and he and she are a couple. He has never really identified as bisexual but essentially identifies as demisexual just with me. He has admitted in the past that he is less sexually attracted to me and it definitely shows. Emotionally I am very happy with our family (we all live together with 2 kids) but sexually I need more. I've recently asked to open the relationship which he is fine with, but is it bad to just want an outside relationship predominately for sexual gratification? I require emotional connection to be intimate with anyone, but I'm not looking for a long term relationship I don't think. Am I wrong for wanting or looking for this?
You are vastly overthinking this, my friend! Your partner is okay with it, and it’s something you want - you should pursue it. Our culture has a lot of weird moralizing baggage around seeking “sexual gratification,” but there’s nothing wrong with pursuing that kind of fun, pleasurable experience. Your partner has another person he has sex with; if it’s possible for him to have sex outside his relationship with you in a healthy and consensual way, it’s clearly possible for you. You would not be hurting anyone. Go for it!
Be careful about setting arbitrary or prescriptive limits on whether you plan for it to be an emotionally committed or long term relationship. Often, those are promises we can’t keep, whether we make them to ourselves or our other partners. Be up front with the people you meet that you’re primarily looking for an emotional and sexual connection that can stay ‘casual’ indefinitely. And make sure you check in with your partner and metamour about what measures everyone needs to take to stay safe, since you’ve been a closed triad and now will be exposing everyone to a new set of sexual health risks.
I also want to say something about the line in your letter that you’re not familiar enough with “the lifestyle” to give a specific term to what you’re doing. Friend, you’ve been living together as a happy, functional family for ten years, and you’re raising kids together! You’re a subject matter expert! This is one reason that I really don’t like the tendency in the polyam crowd to want to come up with a specific term for every little thing - it implies that there’s some sort of esoteric knowledge that makes your polyamory more “real.” This isn’t black magic, and it’s not a secret club. You are living “the lifestyle” more fully and successfully than many, many people! You did a great job explaining and defining what you three are, and do, and have. There’s nothing missing from your language or expression!