Usually people know if they want to have kids or not. And yes it can change many times. Some think they don't and are delighted with surprise babies. Some think they do and then they sort of hate parenthood. I know all these types.
For me, I never wanted kids. I didn't really like random kids. I REALLY didn't like the kids I knew. Meh. I figured, I'd just keep being the happy go-lucky, hard-working NYC chick I was. My ex was the same way. He didn't really like or want kids.
Then one day I was about..33...and I saw a lady my age with a toddler on her hip and I got a physical, fluttery cramp, like a literal biological reaction. Suddenly my mind was flooded with "Holy cow, am I having kids ever or what??!" In almost no time, I had undeniably decided. Not so much that I wanted kids...but that I knew FOR SURE I'd regret it one day if I didn't have them. And I have a big, scary capacity for regret.
My ex was a boyfriend at the time who did not want to commit. I broke up with him stating, "These last four years have been great, but I want to have kids one day so I need to free myself up." He was like, "Huh??! What happened?!" He begged and pleaded for me to stay and NOT have kids and I said "No. Beat it." So he proposed and I was pregnant soon after. We had three kids, he was always a cheater, and now we're divorced and I'm a single mom and he's an excellent co-parent. When he's rarely around-he travels non-stop.
I LOVE LOVE LOVE LOVE being a mom and having three kids-even by myself-more than anything I could ever fathom. They are so fascinating and rewarding and have broadened my scope of life infinitely. I'm not a child-centered person who descended into a kid bubble. We're out in the world doing everything and they have to keep up. I vowed not to let my kids run me ragged and they are well-disciplined, little mature, independent, loving people. It's amazing to have them in my life. I was worried my creativity as an artist would be stunted, but it has improved tenfold.
But if I had never had kids, I would have had a rewarding life too. But definitely huge regret. It's just how my self-torturing spirit operates. I could tell by the pull in my gut. I had mine at ages 35, 37 and 39.
You still have time to wait and see how you feel.
To be honest, having kids AND an amazing relationship with an amazing father in the picture is so super magical..I don't know how anyone could pass it up. Sometimes I see my friends in happy marriages who actually have HELP with the kids, and I'm like, 'Wow, I can't even imagine how amazing that must be." But just being a happy couple works too for people. You have to make a choice and decide to be happy with what you choose. And if you're on the fence, do what makes your partner happy.