A member number in DQ6 (broker information) for sponsored sub-participant cannot be acquired from a login ID under the sponsoring sub-participant.
To acquire a member number of a sponsored sub-participant, a login ID under the relevant sponsored sub-participant needs to acquire DQ6 (broker information).
For details, please refer to “Subscribing and the Latest Information Query” of "J-GATE3.0_Connectivity_Manual_Commonalities_part" and “3.3 DQ6 Broker Signatures (Broker Information)“ of "J-GATE3.0_Connectivity_Manual_Business_Message_part".