First let’s get terms clear.
Godparents are always Catholic. You only need one.
With a godparent (remember, always a Catholic) you may have a Christian witness – that is a non-Catholic who has been baptized in the name of the Father and of the Son and of the Holy Spirit. That mean some people are automatically excluded even if they identify themselves as Christian (Mormons, Salvation Army, many Pentecostals, etc).
While in the ceremony itself you will not see a differentiation between the godparent and the Christian witness, rest assured that the Church sees a great difference. The CW has no role except to be a witness of the Baptism and to testify to it having taken place if the need should ever arise. The godparent, OTOH, should be aiding the parents in their duty to raise the child Catholic.
If you want to call that Christian witness a godparent within the family is up to you.