I have read the whole thread and answers with a great interest.
I was never maternal when younger, got married quite late in life and we then decided that we would like children.
Tried and then went to doctors, had all necessary tests done and I found out that, after suddenly becoming very maternal, (mid 30's), I could'nt have a child.
It broke my heart as I have a brother 4 years younger than me and even though we fought like cat and dog when younger, just let anyone else have a go at either of us!!!!
I got really upset by people who we know asking us when we were starting a family as "You aren't getting any younger", but have now come to terms with it and just ignore the comments.
My husband was an only child, but was brought up with his cousin and considers her almost a sister and she has 4 kids, 3 boys and a girl and she is the only person who has never asked me the reasons why I have not had a baby.
I am lucky. I get on with her kids really well, they dont call me auntie, but consider me their auntie and tell their friends and boyfriends/girlfriends this. And yes...... I spoil them rotten!!
I think if you only want one child, that is your decision, you may decide differently in the future but you sound as if you have a wonderful relationship with your child and that is something to be really, really grateful for. People can be very unkind, even when they think they are being well meaning. I'm actually glad that I am now approaching my mid 40's and do not get the question as much, because at one time, when asked I used to go home and just cry over it.
It's strange, even though I can't have kids, I still get that maternal "pull" when I see a baby, but hey, thats life.