name a office holder whose predecessor is khan abdul wali khan and has son named bilawal bhutto zardari ?
SELECT DISTINCT var_uri where brack_open var_uri dbo_predecessor dbr_Khan_Abdul_Wali_Khan sep_dot var_uri dbo_child dbr_Bilawal_Bhutto_Zardari sep_dot var_uri a dbo_OfficeHolder brack_close