The new (1983) Code of Canon Law is quite specific about the qualifications of godparents.
First, they cannot be the parents of the child since parents already have a unique and special relationship with their son or daughter. Second, godparents have to be sixteen years of age or older. Third, they have to have been confirmed and made their First Communion. Fourth, they have to be practicing Catholics.
What does it mean to be a practicing Catholic? First, you should be a registered parishioner in your local church and attend Mass every week and on Holy Days of Obligation. Second, if married, the marriage has to be recognized by the Catholic Church as being valid. Therefore, divorced and remarried people without the benefits of annulment are not permitted to be sponsors. A person who is married outside the Catholic Church without permission is also in an invalid marriage and cannot be recognized as a godparent.
Catholics who do not regularly go to Mass and rarely, if at all, go to confession are not suitable candidates. This is not a question of whose turn it is to be godparent. Johnny or Joey might be the brother of one of the parents, but his relationship as uncle of the baptized is not sufficient in and of itself for him to be godfather.
If he does not go to Church, if he lives an immoral lifestyle, if he espouses opinions and values that contradict Christian doctrine (racism, abortion, promiscuity, drunkenness, etc.), then he should not be asked to assume the sacred duties of godparent.