When you have followed the above instructions carefully and are sure you have baptized properly, never under any circumstance repeat the Baptism on the same person. It is a sin to try to baptize more than once when you know Baptism can be given only once. The sight of the person dying and the fact that you are called for the first time may cause you to be somewhat excited; but be calm, remember the importance of the Sacrament, and you will administer it as directed. Parents should not baptize their own children in case of necessity, if there is any other person present who can validly do it. Remember those who administer Baptism contract a spiritual relationship with the person they baptize (not with his parents). If they wished, years afterwards, to marry the person they baptized, they must make this relationship known to the priest.
Sponsors are not necessary in private Baptism. A person may be sponsor for a child in Baptism without being present at the Baptism, provided someone else holds the child in his name and answers the questions he himself would answer if he were present. Such a sponsor is said to stand for the child by proxy, and he, and not the one who holds the child, is then the real godparent when, at the request of the parents or priest he has consented to be sponsor.
160 Q. What is Baptism of blood? A. Baptism of blood is the shedding of one’s blood for the faith of Christ.
Baptism of blood, called martyrdom, is received by those who were not baptized with water, but were put to death for their Catholic faith. This takes place even nowadays in pagan countries where the missionaries are trying to convert the poor natives. These pagans have to be instructed before they are baptized. They do everything required of them, let us suppose, and are waiting for the day of Baptism. Those who are being thus instructed are called Catechumens. Someday, while they are attending their instructions, the enemies of religion rush down upon them and put them to death. They do not resist, but willingly suffer death for the sake of the true religion. They are martyrs then and are baptized in their own blood; although, as we said above, blood would not do for an ordinary Baptism even when we could not get water; so that if a person drew blood from his own body and asked to be baptized with it, the Baptism would not be valid. Neither would they be martyrs if put to death not for religion or virtue but for some other reason—say political.