Is there a list of how many kids must character have in order to kid npcs start apearing ?
Check here:
This was the last time I wrote them all down, but it was quite a long time ago. There are many more of them in the game currently. I'll try to remember to update the tally again at some point. So basically there are three types of kids;
Kids that appear when the Total Kids counter gets high enough (this can be checked at the bookshelf in Raptor's room)
Kids that appear when a certain character has enough births. For example, a new child will appear when Kath has given birth 16 times, as you can see on the list above.
Lastly, kids that appear when the Elf population/breeding level gets high enough. You can check this number on the sign at the elf breeding ranch. I believe that having the Elf Goddess give birth also increases this number, but I'm not looking at the code right now, and I would have written this over a year ago. So I can't say for 100% sure if she does or not. Should be pretty easy to test if you're not sure.
When the Elf population goes up to 35, the maximum number of kids in the village will appear. If you sell enough elf slaves, the number of kids in the village will go back down. And then you can bring it back up again.
Technically there's a fourth thing to consider. When the Monster Power level goes up, more monsters will appear on various maps. This can be raised by having the monster breed with various girls, but it will also increase just by talking to your monster allies (you'll hear a chime the first time you speak to them), and donating money to the war chest for your monster raiders.
As noted, I'll just reiterate;
There are more kids than the ones written on this list. This was just the last time I made a tally of all of them.