Can you claim foster kids on taxes?

Last year, we were told you could, as long as they have been in your home six months, but ours hadn't at that time. This year, the woman that is preparing our taxes just called and said although they have both been in our care over six months, we cannot claim them unless they have a social security number. They don't have social security numbers. They are babies and have been with us since early on. Anyone know anything about this?