Asking for someone else's birth certificate in Spain
If you need to request a birth certificate of another person, it is necessary to know that it is a legal procedure in which anyone requesting registration information is presumed to have a legitimate interest in doing so.
However, there are various exceptional cases in which unless a legitimate interest is justified, such as in the case of adoptive parentage, sex correction or change of surname, you will not be able to access them.
In all other cases, a third party can request it in the Civil Registries of Spain. (In the case of minors, the applicant must be the father, mother or legal guardian).