1) the fact that I just can't seem to get super-excited about having a baby...
...Here's my question: While I'm tentatively secure in my decision, and really enjoy my sister/brother's kids and my friends' children, I always end up feeling like the young, immature one next to my family and friends with kids.
Welcome, Cleowin!
Your "just can't seem to get super-excited" comment is classic. There's plenty of reasons not to have kids (the environment, your budget, health reasons), but somehow "I just don't wanna" should be as good as any. Parents and their talk about parenting sometimes remind me of religious fundamentalists...they have a verse or passage for every argument, many of which contradict each other. When they say it's the toughest job in the world, and then also more or less imply it's something that everyone should do, I just shake my head.
When your nieces, nephews, and young cousins get older, things will get easier for you --- for several reasons:
a) You'll be older and more sure of yourself
b) The kids themselves will be into the tween/teen years, a lot harder on their parents, and looking for other relatives (like cool Auntie Cleowin) to hang with as they start to distance themselves from their parents
c) The parents will be past most of the "romance" part of parenting, which seems to accompany pre-adolescent kids. It changes, believe me (at the risk of boring the rest of the folks on this list, let me add, Cleowin, that I'm a high school music teacher). Parents of little kids band together and talk about every last little thing, do playdates together, etc....parents of teens hear about a fellow parent friend's troubles with their teen, and basically say "Wow...sorry to hear it...sucks to be you!". It probably has to do with the idea that babies are a lot more alike than teens are.
My brother converted to (reformed) Judaism for my sister-in-law. When she was done having her twins (enough for her!), she asked me if I'd like to have a pile of books she'd collected on the decision to have kids or not. The two of them had had a terrible time with infertility and were just about to throw in the towel (maybe adopt) when they got the news about the twins. She was very non-judgmental about it, saying "These books just help you ask the questions...they don't suggest an answer. I always knew I wanted to be a mom, but once I hit infertility, I wanted to ask myself just how important kids were to me. Turns out...pretty important".
I was pretty shocked; I'd expected that if they'd said anything, it might be kind of condescending, in the "I'm a parent, you're not", older sibling type way (doesn't help that I *am* indeed the youngest of three). Nothing of the sort.
I have received poor treatment at the hands of other parents --- mostly acquaintances, not friends, thank goodness.
As time goes on, the "environmental" reason for not having kids will probably become more important, with nearly 7 billion on the planet now and projections that we'll go a lot higher before we level off, and species going extinct every day...if an acquaintance gives you grief, you'll be able to say "Hey --- the fact that I chose not to have kids makes life for your kid that much better. Next question?". If it's a friend, something a little more in-depth would be in order, for sure...
Elise