The family story often is of three brothers who immigrated to America, rarely two or four or five or six. Sometimes one is lost at sea during the voyage over, or one went north, one went south, and one headed west, never to be heard from again. There are rarely any sisters involved in the big move across the ocean.
Be wary of the three brothers myth. Confirm through your research that there were, in fact, three brothers, that the three brothers were indeed brothers and not two brothers and an uncle, for example, or that the three brothers were not just three men with the same last name.