The crossword solutions for the term DAD, TO GRANDPA are SON (3 letters). The term 'DAD, TO GRANDPA' is a way of referring to the relationship between a father and his father, or a SON and his grandfather. This relationship is often referred to as a generational bond, and it is one of the most important relationships in many families. The term SON (3 letters) is a reference to the SON in this relationship, who is the direct descendant of the grandfather.