Yeah but, What if they have got Spanish blood (DNA) and have never been to Mexico? Mexican is Indian and Spanish. Indian is Aztec, Olmec, Toltec, and so forth and Spain includes Jews, and various other groups.
Wonder if I count?
I’m 19% Iberian according to my ancestry.com DNA profile.
(I’m also 13% west African, 13% German and 6% Taino, the Indians of Puerto Rico.)
The rest of me is a smattering of different European ethnicities.