Must the wife's guardian be present when the marriage contract is renewed, and if he is absent, is it permissible for her brother (20 years old) to be her guardian?

Divorcing a wife with whom intercourse has not occurred is an irrevocable divorce because she is not required to observe an 'iddah (definition) (waiting period), and she is entitled to half of the named mahr (dowry). To remarry her, a new contract is required, fulfilling all conditions, including the presence of the guardian (wali) and others. It is permissible for the guardian to delegate someone else via phone. The brother cannot be the guardian for his sister if the father is alive, unless the father delegates him.