In spanish-speaking countries, we use our Father's name as the last name. Following this one is the Mother's name, which is only sometimes included. The middle name is used even less often, and unless it is a compound name, only the first name listed is assumed not to be a family name. For instance, if my name is shown as "Cristóbal Sifón Andalaft", people should refer to me as "Cristóbal Sifón", not as "Cristóbal S. Andalaft" as would be the case for english-speaking countries. For more on this, see, e.g., Wikipedia.