請教8老師：how many are I-824 needed per each sibling's family

我申請弟弟夫妻 和姐姐自己移民美國，收到I-797 批準通知。I-797 說下一步申請I-824由USCIS  送申請到NVC. Do I file ONE I-824 only for my brother and his wife; and another for my sister ? I read the I-824 instructions, for part 2- reason for request (1.d- USCIS to send my approved immigration petition to the NVC).  There is no place to put the spouse for part 2-1.D. in I-824 form.

I searched 移民論壇 on I-824 for all the replies you helped other people, and can not find that how many I-824 are needed per each sibling's family.

Thank you so much in advance for your help.