If they don't ask, when do you tell them?

[PrettyCandles]

Nearly-8yo ds1 knows where babies grow, and how they come out, but has never asked how they got in there in the first place.

Do I wait until he asks (my usual strategy), or do I bring the subject up myself?

By what age should a boy know this sort of thing?

6.6 year old ds1 knows that Daddy has seeds and that they come out of his penis. He knows the seeds join with an egg in Mummy and make a baby and he knows where the baby comes out.

What he's got no interest in knowing is exactly how the seeds meet the egg! And I'm waiting until he asks...