My boyfriend is from Ghana he has been in the states since he was 12. How do I find out if he is a legal citizen I don't want any surprises after marriage. Didn't want to be to blunt asking

Ask him ? Does he have citizenship papers, or a green card, visa, passport. He can show you his status when you ask to see it.

A lot of people came to US with their parents when they were very young, but they don't have legal status. It doesn't hurt to ask... and make sure the documents he provides are not fake ones.