I never wanted kids at ALL until I was 28/29 years old. Now, I want at least one child. Being that I'll be living in a host country where I do not speak the language, I feel like I can only deal with one.
It also helps when you find the right person.
Before wanting 3+ kids, you need to be ready for the expenses. My brother earns about 75,000 a year and he still gets strapped for cash at times (he has two toddlers).