I would probably be too mean about it and deserve a spot in e-Hell myself with this;
'Oh mom don't be silly, I got myself fixed last month. Didn't I tell you?'
But in all seriousness, if you don't want kids, I whole heartily congratulate you for that decision. It is a very mature thing to do.
I see too many people with kids they didn't really want, but only got because it was 'expected.'
Heck, even my mother only had me because she remarried, and my dad really wanted to have kids too. And boy if I did not hear it every other day during my teens that she wished she never had me. To make matters worse, I was a girl, so she of course 'had' to have a fourth one, my brother, just to get it right
So that's two kids she never took care off because hey, she never wanted them in the first place.
And yes, your boy does sound like a keeper