[elboru]

Really? from what part of Mexico? I'm Mexican and I've never heard someone addressing their father as "sir" (señor) not even "father" (padre) we usually use "dad" (papá), even using "usted" instead of "tu" is not common anymore. But then again Mexico is a really big and diverse country, so there must be zones where that could happen.

[eboyjr]

It's interesting because in some parts of Northern Mexico, you would think that use of "tú" didn't exist. NO ONE uses it, not even relatives or husbands and wife.