WordNet
n. your foster brother is a male who is not a son of your parents but who is raised by your parents
Usage examples of "foster-brother".
Even Sadik the Mouffetish--Sadik, who had four hundred women slaves dressed in purple and fine linen--Sadik, whose kitchen alone cost him sixty thousand pounds a year, the price of whose cigarette ash-trays was equal to the salary of an English consul--even Sadik, foster-brother, panderer, the Barabbas of his master, was silent and watchful to-day.
She hardly heard the polite words of those two foster-brothers, Balin and Balan-which of them was the son of the priestess of the Lake, then?
After the amiable fashion of French mothers, she had placed him out at nurse in a village in the neighbourhood of Paris, where little Rawdon passed the first months of his life, not unhappily, with a numerous family of foster-brothers in wooden shoes.