 'Abd al-Muttalib left the Banu Hashim and went with the Quraysh supporting them against 'Abu Talib.This state of affairs continued for two or three years, until the two clans were exhausted, since nothing reached any of them except what was sent secretly by those of the Quraysh who wished to maintain relations with them"....These days were very hard with them and very often they had to feed on the leaves TALH or plantain" 

Thus, this boycott included even Hashemites that had not accepted Islam.