not in first world countries - you don't want the death rates of say India on the roads
I suggest you google for "fiets met kinderzitjes" (bike with child seats) to get examples of how you can transport 2 small children on one regular bike.
Once the children get older they can get their own bike. If you need to transport more than 2 children, get yourself a second parent or a bike that's designed to take cargo (yes I just called your children cargo).
My mother raised me and my sister on her own, using just a bike.
At least in Amsterdam where I biked around a bit, it seemed flat as a pancake.