Knowing ... How do you know?

How do you know if you want to become a parent?
When do you know you want to be a parent?
How do you know you'll be a good parent, if you choose to want to become a parent?
Does your biological clock tell you that it's time to be a parent?
Is there even such a thing as "your biological clock"?
And not knowing or not wanting to became a parent, does that make you "a bad person"?

I've had a lot of conflict and discussion in my life about when are you two having babies? We reply with we're not, we don't want any, to finally now we are by far not ready and we're not sure we really want any. After any of those response we get The QUESTIONS and astonished response...
You be so alone!
You'll want them in due time.
Are you kidding me?
What about when you get old? Who will take care of you?
How will you function if everyone else is having kids and you don't?
What will you do when they want to vacation with you, but the kids have to come along and you don't want them too?
Do you not like kids?
I can't believe you of all people do not want to have children!
Is this like for sure?
Oh, you're just being silly! You'll want them sooner or later.

It goes on and on and on and on and, well you get the point. What if I don't thought? What if I think I'll be happy and find borrowing other peoples kid and moving on with my life is OK? What if I want to be "the incredible AUNT MARGARIT? Does this make me a inhumane person? Does this make me weird? (weird, well maybe)

This weekend I was hanging out with the family for labor day. Some how I'm sure the question got brought up again and my sister-n-law mentioned she thought her son might be sterile. It runs in the family and you may have that same gene, she tells him and his girlfriend. He and his girlfriend of 7 months were so sad, so upset, and concerned about what they should do.

He's 19 and she 17. How in the world do they know that they want to have kid? I mean they've not faced graduation, college, marriage. They've not even got the opportunity to see what 21 feels like when you party like you're a rock star. How do they know? Why are they even talking about it? But more in point how do they know they want kids when in actuality they are still very young and don't even know what they want to eat for breakfast?

The real point is ... How do they know and I (28, married, housed, educated) don't?