Formal:
* Irmão: This is the most common and neutral way to say "brother."
* Irmão mais velho: This means "older brother."
* Irmão mais novo: This means "younger brother."
Informal:
* Maninho: This is a more affectionate and informal way to say "brother," often used between close siblings.
* Irmãozinho: This is a more diminutive form of "irmão," also used affectionately.
The best way to say "brother" in Portuguese depends on the specific situation and your relationship with the person you are talking about.