I was born and have always lived in Mexico, as were my parents. But my mother recently mentioned that her mother (my grandmother, since passed away) was born in the United States (to Mexican parents). That means my grandmother was a U.S. citizen. Is there any chance that her citizenship could pass to me?
U.S. citizenship does not pass directly from a grandparent to a grandchild—but don’t stop there when looking into this matter. If your mother acquired citizenship from your grandmother, it’s possible that you then acquired citizenship from your mother.
“Acquisition” of citizenship is a legal concept, by which some people who were born abroad to a U.S. citizen parents automatically become U.S. citizens themselves, if certain conditions are met. (A related legal concept called “derivation” of citizenship applies mostly to people who are already green card holders, but from what you’ve described, this probably doesn’t apply to you.)
The difficult part about the laws on acquisition of citizenship is that they have changed many times over the years; and the law that applies to your mother and then to you depends on first her and then your dates of birth.
Let’s say, for example, that your grandmother gave birth to your mother in 1975. Under the laws in effect then (described in Citizenship Through U.S. Citizen Parents (If You Were Born Between 12/24/1952 and 11/13/1986)), your grandmother would need to have lived in the U.S. for a minimum of ten years, with five of those years occurring after the age of 14, in order for her to pass citizenship to your mother. (We’re assuming that your grandfather was not also a U.S. citizen—if he was, a different law applies.) Your mother would not need to have lived in the U.S. at all to gain citizenship from her mother—but she probably would have in order to pass citizenship to you, as described next.
Let’s say that you were born in 1996. If your mother is indeed a U.S. citizen, but your father is not, then for you to acquire citizenship from her, she would need to have been a U.S. resident for at least five years, with two of those years being after the age of 14. (For details, see Citizenship Through U.S. Citizen Parents (If Born Between 11/14/1986 and Today).)
As you can see, citizen by grandparents is a long shot, and may depend on proving more than one person’s long-term residence in the United States. See an immigration attorney for a full personal analysis.