I've never imagined myself to be the monogamous type; I always thought I'd only enjoy being in open, casual relationships. I've never imagined myself settling down (and I still don't). When I imagine my ideal future, kids and marriage are never a part of it.
I'm not opposed to being in a serious monogamous relationship with someone I really love. I am opposed to the idea of government-mandated monogamy. Why do you need a piece of paper that says you're in love and seriously devoted to this other person? Why isn't our word enough? If you need a piece of paper saying you're LEGALLY bound together to feel comfortable in your relationship, I literally don't understand.
You should be in a relationship with someone you can totally and completely trust.
I used to be really opposed to monogamy, but more recently, I'm not as opposed to the idea. I've found a man that I really adore and I'm very happy in a monogamous relationship with him. Monogamy used to terrify me, but I discovered it's not so terrifying when it's with someone whose company I really enjoy.
Even though I understand monogamy now, that still doesn't mean I understand marriage. I've never dreamed of having some big, fancy wedding like many of the girls I was friends with in elementary school. They'd be fantasizing about their dream weddings while I was thinking of what I wanted my career to be.
I'm still quite similar. I fantasize about my future career way more than I imagine my romantic life. I don't see myself married with kids at any point in my life. I might have a serious monogamous relationship for a long period of my life, but I have no intention of ever getting married. I don't need government-mandated monogamy to feel comfortable in my relationships and with who I am.