name a office holder whose predecessor is muhammad mian soomro and has son named bilawal bhutto zardari ?
SELECT DISTINCT var_uri where brack_open var_uri dbo_predecessor dbr_Muhammad_Mian_Soomro sep_dot var_uri dbo_child dbr_Bilawal_Bhutto_Zardari sep_dot var_uri a dbo_OfficeHolder brack_close