Can supererogatory prayers be performed on behalf of one's father, brother, and sister, with the intention of their healing?

It is not legislated for anyone to pray the obligatory or supererogatory prayers on behalf of another, except for the two rak'ahs of Tawaf (definition) during Hajj or 'Umrah (definition). Prayer does not admit proxy, and this is the consensus of scholars. It is legislated for the Muslim to increase in acts of obedience, worship, and supplication for the sick, as drawing near to Allah through supererogatory acts is among the reasons for the answering of supplication. It is also legislated to perform ruqyah (definition) for the sick with the Qur'an and lawful incantations.