Most hispanic people use two last names? How can that be? How can you have two of the "last" thing? Well, in Spanish a last name is not called a last name. In Spanish, the last name has a name of its own, it is called apellido. And, it does not mean "last" or anything like it. So, when you talk about someone's last name you talk about their apellido or apellidos since there are two. The two apellidos are referred as the first apellido and the second apellido.
My first apellido, Pérez is the first apellido of my father and my second apellido, Quiñones, is the first apellido (called maiden name in the US) of my mom. So, my apellidos are: Pérez Quiñones because...
My Dad: Pérez Rodríguez
My Mom: Quiñones Alamo
Yours truly: Pérez Quiñones
So, what happens when you get married? Nothing changes on the male, and the female changes her name as follows. Her first apellido is still the same (her father's first), but her second apellido changes to that of her husband. The word 'de' is added between the two last names to indicate that the second last name is her husband's. My wife's last name before we got married...
Her Dad: Padilla Rivera
Her Mom: Falto Pérez (no, she is not related to my father)
My Wife: Padilla Falto
After marriage, my wife's apellidos became: Padilla de Pérez.
Me: Pérez Quiñones
My Wife: Padilla de Pérez
(actually, she never changed her apellidos, so she is still Padilla Falto, but you get the idea of how it usually works).
Confused yet? Hang on, there is one more thing. What will happen when we have children? Well, the whole circle of life begins again (literally). For example, our children's apellidos will be: Pérez Padilla. If you noticed that we are back to the beginning of the explanation, then you have been reading this way to carefully. Get a life :-)
Our children: Pérez Padilla
Finally, to avoid confusion in computerized systems that automatically take the last word in the name field to be the last name, a lot of hispanics hyphenate their apellidos, as I do with mine Pérez-Quiñones.
Now you know that Gabriel García Marquez is the son of Mr. García and Mrs. Marquez, or more formally the son of Mr. & Mrs. García Marquez. And if you send a letter to the family of Arancha Sanchez Vicario, you would address it to the Sanchez Vicario Family.