"У меня большая семья, у меня есть жена и двое сыновей."
Why "сыновей" and not "сына"?
After all
1 - Nominative
2 - Genitive (singuar)
3 - Genitive (singular)
4 - Genitive (singular)
5-10 - Genitive (plural)
So we're talking about two sons here. Should be genitive SINGULAR, right?