Book about the 'facts of life' for a 3-year-old

[Dashie]

I'm hoping for some recommendations for a simple book I can read with my 3-year-old to answer his questions about where his baby sister came from and why mummies don't have willies!
He's coming up to 4 and loves being read to, very chatty, and retains information like a sponge.
I've looked at some old threads on here and have seen suggestions for 'Mummy laid an egg' and 'How did I begin'. I've also seen a possible one called 'Where willy went'.
Are any of these suitable/good for a 3-year-old? Is he actually a bit young for these discussions? I don't want him to grow up too fast but at the same time I'd prefer that he just takes it on board with all the other fact books he likes to look at rather than it become a taboo subject that becomes more difficult to talk about as he gets older.
Thanks for any advice!

"It's not the stalk" is a nice one.

I mean stork obviously.

My almost four year old likes "Where Willy Went " . I think it's a bit strange to turn the process into a fictional story but it seems to hit the mark with both my boys . I have shown them YouTube clips of digital baby development of conception to birth .They were fascinated after seeing a foal born . We haven't discussed the deed , I just say the baby starts with a part of the father and the mother .

Yallahabibi, I hadn't thought of YouTube, that's a great idea. Thank you!

Thanks Pirate, that looks like exactly what I need.

I bought Mummy Laid an Egg and WWW and just read them/had them on the shelves as normal bed time stories. DD age 5 has seen them from under 2 (when dc2 came) and has a good but not overtly detailed understanding of it all.

Mappemonde, that's what I'm thinking of doing. I'm hoping that he will read the books without it becoming a big deal.