His father's from Mexico, that gives him closer ties to Latin-American cultural heritage than it does to Spanish cultural heritage.>>102644506
I don't know where you're getting your definitions from, but from what I'm reading that meaning of mestizo isn't really in use anymore today, rather being a term for anyone with ties to Latin-American culture, regardless of descent.
Also, even it did still mean that one of his parents is from Native-American descent, couldn't his dad qualify? It's not hard for me to see his family having strong native roots and he certainly looks the part.
In addition to that, going by the original meaning, castizo would refer to someone with a mestizo and a white parent, and it seems questionable at best that Marco's dad is mestizo.
I also don't know where you're getting that latino is an ethnic term? It seems to refer to people of Latin-American cultural heritage while, as I explained above, hispanic is the same but for Spanish heritage. Doesn't the former apply more here?