Adding prefix to a name
For Japanese names, I know about adding -san to them. But once, I heard a person (who isn't Japanese) addressing a Japanese person as nii. And the Japanese person seems happy? I know nii means 兄, brother. But I know they are not related? Since one is Japanese, and the other is not. So does adding 兄 means you can drop the -san at the end? Thanks.Or does this just means that they are close?

Question

Adding prefix to a name
For Japanese names, I know about adding -san to them. But once, I heard a person (who isn't Japanese) addressing a Japanese person as nii. And the Japanese person seems happy? I know nii means 兄, brother. But I know they are not related? Since one is Japanese, and the other is not. So does adding 兄 means you can drop the -san at the end? Thanks.Or does this just means that they are close?

Answer

In this case, "nii" means "兄" (older brother). Maybe it is nickname what you heard. For example, there is a man whoes name is Hideo and he had a younger brother. His younger brother call like "Hide-nii". Other case, a person whoes face look like older than same age or a person who is relyed by his freinds like real brother, is called "Aniki" or "○○○-nii" in the classroom.
You should not call "○○○-nii" to a person who looks like older than you and meet a few times. In this case, you should use "○○○○-san".
You can only call a person who is a close friend.
Can you understand what I want to say?

Answer

from dictionary:
兄 【にい】 (n-suf) (1) (fam) used after the name of someone who is an older brother figure; (n) (2) (See お兄さん) used with various honorifics to mean (older) brother