I have always had 6 kids. To do it I:
1. choose peeps in their early 20's if possible. especially in
the first couple of generations.
2. i select peeps where at least one is a definite for kids and
the other must be at least a would be nice prefer both to be
definitely's though.
3. I start for kids as soon as female has gotten one promotion and
pause the game every time i leave it until i have 6 kids.
4. I begin trying for the next baby as soon as I can after the mom
is through nursing the one before.
5. i don't let arguments stop me lol keep dropping them together
until they comply. If don't get one on that try try again in
15-30 min.
6. in later generations i give baby boost to both when they marry


has worked for me always get 6 kids to choose the next generation from.