By combining English and Spanish, her two native languages. :)
It might be said that Anaya´s memoir is a celebration of the "elder". That is why, it is more appropriated to use the term "grandfather(s)" in plural, to make reference to all of them and not just his. It includes older generations and future generations. His father is just an example to illustrate what he is talking about.
the answer is : it is written in your own words