Question: "In our services we often speak of "our holy and God-bearing fathers, and all the saints..." I understand that the reference is made to the Church's founding fathers, but who is meant specifically? All the Apostles? Just Peter and Paul?"
This is an interesting question. Like many seemingly simple questions, it is not as simple as it might seem at first glance. On the one hand, you might think it could refer to all of the saints that have gone on before us, but then after they are mentioned, we then hear "and all the saints," which would be redundant if they referred to the same exact group of people. So just from the meaning of the words alone, I think we can say that we are talking about some group of saints, but not all of them.
I would say that it certainly refers to the Apostles. No doubt this also includes the Church Fathers... who are actually considered saints by the Church. Often the phrase "Church Father" is applied to any important Christian writer during the patristic period; but those, like Tertullian and Origen, that are not considered saints because their teachings contained significant errors rejected by the Church, can only be called "Church Fathers" in a very loose sense of the term, and are not what we are talking about here. It would include the Fathers of the various Ecumenical and Local Councils that the Church has received as having ecumenical authority... but again, only including the participants of those councils that are saints. We may not know all the names of these saints, but we do know the names of some that are definitely not saints, and so they would not be included.
But are we excluding saints of the Old Testament, and does this exclude women? Not at all. In many languages a masculine word is often used in a way that is inclusive of males and females, and that is true in this case. For example, we have two Sundays of the Fathers that are specifically focused on the Saints of the Old Testament -- the two Sundays prior to Christmas. On the Sunday of the Holy Forefathers (which is two Sundays before Christmas), we not only sing about the many prophets and saints of the Old Testament who were men, but in the canon of the Ninth Ode, we hear about some of our Foremothers:
"By Thy might, O Lord, Thou didst of old make Thy daughters powers: Hannah and Judith, Deborah and Huldah, Jael and Esther, Sarah and Miriam the sister of Moses, Rachel and Rebecca, and Ruth the exceeding wise."And on the Sunday before Christmas (which is also called "the Sunday of the Holy Fathers" and sometimes "the Sunday of the Genealogy," because we read the genealogy of Christ from Matthew 1 at the Liturgy), we also sing at the Praises:
"The Virgin Theotokos, she who through the ages hath been preached on earth by the prophets in their utterances, she whom the wise patriarchs and the assemblies of the righteous proclaim, with whom the comeliness of women joineth chorus: Sarah, Rebecca, Rachel and Hannah, together with the glorious Miriam, the sister of Moses. With them all the ends of the world rejoice and all creation rendereth honor, for the Creator and God of all cometh to be born in the flesh and to grant us great mercy."
In addition to the Prophets, Apostles, and the Fathers who have instructed the Church in the Faith, we also include those saints who were ascetical teachers. And here again, we find that this does not exclude our spiritual mothers. For example, in the Sayings of the Desert Fathers, in addition to such saints as St. Anthony the Great, and St. Poemen, we also find the sayings of St. Theodora of Alexandria, St. Sarah of the Desert, and St. Syncletica of Alexandria.
So I think we can say that when we speak of "our holy and God-bearing fathers," we are speaking of those of both the Old and New Testaments, and both fathers and mothers, who helped lay the foundations and build up our faith and our Church, both in terms of their examples and their teachings. And this does not only include those of the distant past, but also more recent examples such as St. Cosmas of Aetolia, St. Nicodemus of the Holy Mountain, the Optina Elders, St. John of Kronstadt, and St. John of Shanghai, and many others. And we will continue to add to their number until Christ returns.