My wife told me that in Persian/Farsi, there are different words for "uncle", "aunt", "grandfather" and "grandmother" that indicate which side of the family they are from (father's brother, or mother's brother? etc.)
Is there anything like that in Spanish? I think not (there's just "tio", "tia", "abuelo" and "abuela"), but would be happy to be proven wrong.
Apparently there is no common way to do this; how about:
Abuelopa (father's father) Abueloma (mother's father)
Abuelapa (father's mother) Abuelama (mother's mother)
Tiopa (father's brother) Tioma (mother's brother)
Tiapa (father's sister) Tiama (mother's sister)