Yes, yes, I know: I have a large backlog of posts and every intention of attacking it Real Soon Now.
This evening, though, Aidan was sitting at dinner and made me proud enough that I wanted to post right away :-).
A: "Dad, why are brothers and sisters not allowed to marry one another?"
me: explanation; he gets genes and DNA at least a basic level, so the concept of recessive etc. was no big deal.
A: "OK. But then how come I can raise only one eyebrow when I couldn't have got that gene from either you or [Jenny] because you can't do it?"
We discussed - briefly! - some possible explanations; but I was just really happy to have him thinking about this stuff and asking questions entirely spontaneously. He got icecream and extra kisses :-)).