at the time of offer and acceptance of the bride if the Qadi metions the groom's brother's name instead of the grooms name and he mentions the grooms uncle's name instead of the grooms father's name and based on that the bride says accept is the nikah valid or do they have to perform the nikah again.
Al-jawab billahi at-taufeeq (the answer with Allah's guidance)
The Nikah is not valid, because she already had knowledge and determined (Niyyah) to marry the groom and not the groom's brother, and whatever the Qadi had mentioned is invalid and meaningless. The contract of Nikah must be performed again with the correct details.
In addition, Both contractors and witnesses must Know the meaning of offer and acceptance in marriage and be aware that marriage is taking place and to whom with, without this knowledge the marriage is invalid.