The Italian word for brother is 'Fratello' and can be used in much the same way it's English equivalent is.
A version of the popular television show Big Brother is aired as Grande Fratello in Italy, and even the slang use of the word 'Bro' in English is mirrored by the Italian use of the words fra' or frate.
The plural of fratello is fratelli, but can interestingly be used to refer to siblings of both genders collectively. For example, an Italian who introduces his sister would refer to her as 'mia sorella' or 'my sister'- but would refer to his brother and sister together as 'miei fratelli' or 'my siblings'.
Etymology
The word fratello can be traced back to the Latin frater and could be used to refer to both siblings, friends and lovers. The Latin root can be seen in English words denoting brotherhood, such as the word 'fraternity'. The word fratello can also refer to a form of brotherhood in Italian, with it's ecclesiastic use commonly referring to friars or monks.
