This means "I love you my best brother my friend". If you mean "older brother" it is "mi hermano mayor".
It is "mejor amigo" in Spanish. If you are speaking of a female, it is "mejor amiga".
In spanish, "best friend" is mejor amigo(a), amigo is for a boy and amiga is for a girl.
If it is a male best friend, you say, "mejor amigo, a."
In Spanish, it means "What is the name of your best friend?"
mi mejor amiga
mi mejor amigo - my best freind
'No soy tu mejor amigo?'
Best friends = mejor amigo(a)s or = o Like your enemy = Como tú enemigo(a)
te amo mi mejor hermano
You would say "Eres lo mejor hermano".
Su / tu / vuestro (a) mi mejor amigo (a) = Your best friendyour my best friend (an illogical sentence)If you meant: 'You're (= you are) my best friend' - Es / eres mi mejor amigo (a)
"Como era Tu mejor amigo" translates to "What was your best friend like?" in English.