The Nikah is invalid without the consent of the father. If they want to marry, he has to be either present or giving the power of attorney to someone who would represent him at the time of marriage.

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  It is the consensus of scholars that the father is the wali in the presence of the son. The other relatives are derived from the distribution of inheritance and how they classified the brother to be closer than paternal uncle and that the uncle is closer than the cousin etc.

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