Bingo.
They have Irish blood.
There is no such thing as Mexican blood.
I had a conversation with my daughter about Mexicans the other night. Started about something stupid, like Mexicans don't have blond hair. I corrected her, telling her there is racism and class warfare in Mexico. Many of those illegals flooding across our border are brown skinned. Lots of successful Mexicans stay put, have Spanish blood, white skin and some with blond hair. Brown skinned ones have mixed or pure native indigenous (indian) blood and detest the purer Spanish blood Mexicans. It's not all the same down there. So yes, there is no such thing as Mexican blood. I had Mexican friends who were pure Yaqui Indian blood and they detested the fairer skinned Mexicans of Spanish descent. Some fair skinned Mexicans I know are quite proud of their Spanish blood and pass for white.
Of course there is Mexican blood.
People have been living in Mexico for thousands of years.