A person may only have one or two godparents (also called sponsors); if two are chosen, one must be male and the other female.
In order for someone to be eligible as a godparent they must:
be chosen by the parents
have the ability and the intention to fulfill the role
be at least 16 years of age, and be a confirmed Roman Catholic, who:
has already received the Most Holy Eucharist,
is leading a life in harmony with the Catholic Faith (including a valid Marriage within the Catholic Church)
will be a good role model for the one being baptized
and be neither the father nor the mother of the child
Nota Bene: A Roman Catholic not in good standing with the Church (i.e., not validly married within the Catholic Church) may not serve as a "Christian witness". See
here.