Is it true that a person who is half British and Half Nigerian has Duel Citizenship in both UK & Nigeria?

Question

And also is it true that they are referred to as "Mullato"?

Answer 1

You will have citizenship from the country that you were born. The other country might grant citizenship, but you have to apply and it will depend on their rules. Most would grant you citizenship, but not all.

Mulatto would be a correct but antiquated term, not many use it anymore.