The best course of action is for him to speak privately about this with his pastor.
The following is my considered opinion as a layperson. I am not an expert, but just try to be a well-read layman. The person involved should consult an expert (ie, his pastor, a canon lawyer, or somebody else who is qualified to render an authoritative judgment on the issue).
From my humble opinion, the validity of a baptism is important enough that if there is any question as to the validity of his baptism in the Protestant community, they may wish to privately perform a **conditional **baptism and conditionally perform confirmation after that conditional baptism.
The Code of Canon Law says:Can. 865 §1. For an adult to be baptized, the person must have manifested the intention to receive baptism, have been instructed sufficiently about the truths of the faith and Christian obligations, and have been tested in the Christian life through the catechumenate. The adult is also to be urged to have sorrow for personal sins.
In your post, you said: He was brought up in a Protestant family who delayed his baptism until he was something like 13 years old. But at that time, he says, he didn’t want to be baptized
Canon Law also says the following:Can. 869 §1. If there is a doubt whether a person has been baptized or whether baptism was conferred validly and the doubt remains after a serious investigation, baptism is to be conferred conditionally.
§2. Those baptized in a non-Catholic ecclesial community must not be baptized conditionally unless, after an examination of the matter and the form of the words used in the conferral of baptism and a consideration of the intention of the baptized adult and the minister of the baptism, a serious reason exists to doubt the validity of the baptism.
Because of the statement that he made to you (at that time, he says, he didn’t want to be baptized), there may be an issue as to the baptism’s validity, according to Can. 869 §2 (note the bolded and underlined text above).
Note the text of Can 869 §1, above. If there is a doubt as to the validity of the baptism, baptism is to be conferred conditionally. A conditional baptism doesn’t hurt anything. If the person was baptised validly before, he just gets his head wet. However, if he wasn’t, it could be the state of his eternal soul.
As for conditional confirmation, Canon 889 says that only a baptized person can validly receive confirmation. If he wasn’t validly baptized in that protestant community, then he could not have been confirmed when he was received into the Church.
**LET ME STRESS AGAIN THAT THE ABOVE ARE OBSERVATIONS FROM A LAY PERSON. THIS INDIVIDUAL NEEDS TO GO TO SOMEBODY WHO IS LEGITIMATELY QUALIFIED TO RENDER AN AUTHORITATIVE OPINION ON THE MATTER. **
But I think the question does need to be asked.