I'm a month away from my 20th birthday and in college, so right now, my answer to that question is "Ask me again in six years." My mom had kids at 20 (she was 20 when my older brother was born, 23 when I was born) and she most likely would have finished college otherwise, so I can safely say that I should finish college before I even think about having kids.
Even then, with how I am now, I feel like my answer to "do you want kids?" would be "no." I just can't stand other people's kids, especially when they fucking cry everywhere. It gets on my nerves and I'm pretty sure I'd have even less patience if I were the parent in that scenario. I mean, shit, I don't even have the patience to put up with my mom's bullshit, why would I have the patience to put up with a kid AND my mom's bullshit simultaneously? And besides, what happens if I get a divorce, the ex-wife gets sole custody, and then I have to pay alimony and child support? I'm a bit of a pessimist, so naturally I spend way too much time focusing on the outcome of the worst case scenario(s) than I should. Even if I DID have the patience to put up with kids, the words "child" and "support" put together in that order are enough to steer me clear away from having kids.
Even then, though, I feel like my parents would pressure me into having kids anyway. They've made it very clear that they want grandchildren, and in particular my mom is the kind of person who will do just about anything to get what she wants. Attempting to make me feel bad for not having kids would be the MINIMUM she would do, and just banking on my older brother having kids isn't an option because he has even less desire to have kids than I do. I guess that'd make me a prime target for my mother's manipulation, that I may possibly change my opinion on having kids but any attempts to get my brother to change his mind would equate to shooting yourself in the foot.
In fact - that's another reason I don't want kids. I always hated how manipulative my parents are, and 1) I fear I'd be just like them, 2) Even if I don't end up being just like them, I feel like they'd exert their manipulative personalities on my children.
However, I may change. I don't know the future. Maybe I'll stop being a pessimistic little shit. Maybe I'll develop some degree of patience. I don't know. Maybe I'll change when I'm like, 28 or something and decide I do want kids. However, I guess my question is if, in the future, I do end up absolutely not wanting kids for any reason, how do I put up with my parents since it'd a "I don't want children but they want grandchildren" scenario?