I might say "My forefathers were Irish". Is there an equivalent for mothers? Could a woman say "My foremothers were German"?
You'd be surprised to know that the female version of "forefathers" is indeed "foremothers".
From Merrian-Webster, the definition of "foremother" is
a female ancestor
However, if one wanted to describe both his/her foremothers and forefathers under the same light, then I suggest you use these gender-neutral synonyms: forerunner, predecessor, ancestor, antecedent, and antecessor. Lastly, I should make note that the word "forefathers" can encompass both men and women. For example, the sentence "My forefathers originated from Africa" can describe the origin of both my female and male ancestors. It's just that many times the word implies a relation to men, but not always. Therefore, the noun is not completely gender-neutral. Once again, from Merrian-Webster, the definition of "forefather" is
a person (especially a man) who was in your family in past times