##Eponym
noun
1.
a person, real or imaginary, from whom something, as a tribe, nation, or place, takes or is said to take its name: Brut, the supposed grandson of Aeneas, is the eponym of the Britons.
2.
a word based on or derived from a person's name.
or possibly a Homonym:
b. A namesake.
However, most of the other definitions of a homonym are slightly different in meaning, so you might have to qualify it; e.g. "parental homonym" or even "cognomenal homonym" if you wanted to refer to any sort of relative.