I have twin girls who are now 10, we've discussed the basics regarding sex, periods etc as questions arose, and they did have a book which I have recently discovered they put in the charity shop bag as they thought it was disgusting!
I overheard a conversation between them the other day that made me think I need to explain further but need some ideas, bearing in mind they thought the book was gross:
DT1 - I've been thinking about this sex thing
DT2 - I know it's gross isn't it, I can't believe you have to do that to get a baby
DT1 - It might not be as gross as we think
DT2 - What do you mean?
DT1 - Well I don't think you have to kiss or anything yuck like that, maybe you just put it in and out and that's it, a baby starts growing.
DT2 - Oh right, yeah maybe.
So, any ideas on how to give more detail without freaking them out.