In regard to a sponsor for Confirmation, the 1983 Code of Canon Law states:
Can. 892: “As far as possible the person to be confirmed is to have a sponsor. The sponsor’s function is to take care that the person confirmed behaves as a true witness of Christ and faithfully fulfills the duties inherent in this sacrament.”
Can 893,1: “A person who would undertake the office of sponsor must fulfill the conditions mention in Can. 874 (listed below):
1: Be designated by the one confirmed, by the parents or the person who takes their place, or in their absence by the pastor or minister and have the aptitude and intention of fulfilling this function.
2: Have completed the sixteenth year of age, unless the diocesan bishop has established another age, or the pastor or minister has granted an exception for a just cause;
3: Be a Catholic who has been confirmed and has already received the most holy sacrament of the Eucharist and who leads a life of faith in keeping with the function to be taken on;
4: Not bound by any canonical penalty legitimately imposed or declared;
5: Not be the father or mother of the one to be confirmed“
Can 893,2: “It is desirable that the sponsor chosen be the one who undertook this role at baptism.”