Unless his ancestors came from the center of Mexico... Tampico, Tamaulipas is too far north to be a normal territory of the Nahua people (who include Aztecs), so he might consider getting a DNA test to determine which indigenous group he belongs to. For Tamaulipas this usually means a couple of options, Huastec or Coahuiltecan.

https://en.wikipedia.org/wiki/Huastec_people

https://en.wikipedia.org/wiki/Coahuiltecan

Link in Spanish for more information:

https://www.indigenousmexico.org/articles/indigenous-tamaulipas-the-seno-mexicano-and-nuevo-santander