During dv entry, it will ask if the applicant is married and if so one has to provide the detail info of the spouse and upload the DV photo of the spouse too. You said you mentioned his wife as a beneficiary, not sure what you mean by that. Are you sure you checked the married button, uploaded his wife's photo and filled in her biographic information? I don't think u did those. and it's your mistake that ruined your brother's chance to come to US; don't blame the US embassy, blame urself.