Bostanai was the son of the exilarch Hananiah. Hai Gaon seems to identify Bostanai with Haninai, and tells that he was given for wife a daughter of the Persian king Chosroes II (died 628), by the calif Omar (died 644). Abraham ibn Daud, however, says that it was the last Sassanid king, Yezdegerd (born 624; died 651-652), who gave his daughter to Bostanai. But in that case it could have been only Calif Ali (656-661), and not Omar, who thus honored the exilarch. It is known also that Ali gave a friendly reception to the contemporary Gaon Isaac; and it is highly probable, therefore, that he honored the exilarch in certain ways as the official representative of the Jews. The office of the exilarch, with its duties and privileges, as it existed for some centuries under the Arabian rule, may be considered to begin with Bostanai.