All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
It is permissible to authorize someone else to conclude one's marital contract. The Messenger of Allaah, sallallaahu ‘alayhi wa sallam, authorized An-Najaashi (Negus) to conclude his marital contract to Ramlah bint Abu Sufyaan both. The story of this marriage is well-known.
Consequently, it is permissible to authorize one's father, brother or others to conclude the marital contract.