T he Spanish nobility, unlike their European counterparts, was based almost entirely on military service. Few families of eminence came from the law, commerce or the church. The great families of Spain and Portugal fought their way to their rank. This may sound primitive on the surface, but it was actually quite fair as it allowed commoners to join the ranks of the nobility through loyal and successful military service. Indeed, many poor families came to prominence and wealth quickly as a result of their successful military exploits.
Spanish arms are inheritable as any other form of property.
Also, illegitimacy did not prevent the descent of arms and titles. The great Spanish families believed that a family pedigree could be more damaged by misalliance than by illegitimacy. Indeed, the patents of nobility of many Spanish families contained bequeathals to illegitimate branches in case no legitimate heirs were found. Illegitimacy in Spain was divided into three categories. Those born of single or widowed parents who could be legitimized by the marriage of their parents or by a declaration by their father that they were his heirs.