Zero vs. definite articles in "filial piety of son to father"
Solution 1:
the filial piety of a son to his father
You need the definite article preceding the noun phrase, nowhere else. Keep the indefinite article in a son.
a son the typical son, any; not the son, not a certain individual.
Whence,
"the (kind of) filial piety (that) a (typical) son (has) to his father.