The advent of genetic technology has produced fascinating questions that force us to examine what “Jewishness” really means. That said, my understanding of the scientific research thus far indicates that while certain genetic sequences (and sadly, increased susceptibility to certain diseases) is suggestive of some Jewish ancestry, it is not determinative.
Even though much of Jewish history is marked by endogamy (marriage within the faith), this has not been uniformly followed throughout different times in history. Also, we can trace incidents (including the Spanish Persecutions of the late 15th century) that forced one’s Jewish identity to be hidden, forsworn (at least publicly), or denied. There are fascinating stories of families, identifying as Catholic and of Spanish origin, who until recent generations had a custom of lighting candles in a basement with no windows on a Friday night. While these stories and genetic indicators speak to a history that is just waiting to be revealed, the consensus among most Jewish authorities is that unless Jewish ancestry is unmistakable, that a conversion process would be appropriate to affirm Jewish identity.
Judaism holds that “Yisrael, af al pi she-chat’a, Yisrael hu” – that regardless of whether a person of confirmed Jewish identity leaves the faith (whether willingly or under duress), that person retains his or her Jewish identity, and can always re-affirm this identity, with no need for formal conversion. That said, traditional Judaism (including the Conservative Movement in which I am a rabbi) defines a person as Jewish either by having been born to a Jewish mother, or having completed a conversion process, including a beit din (rabbinic tribunal’s affirmation) and immersion in a mikveh (ritual bath), as well as (for a male), circumcision (or hatafat dam brit, the drawing of a small drop of blood from the genital area for an already-circumcised male).
Your son’s father and your boyfriend may be able to trace some genetic indicators – but unless they have confirmation that they come from a crypto-Jew family (Jewish matrilineal ancestors forced to hide their Judaism because of persecution, such as in the Spanish Inquisition), then they would likely need to convert to be considered Jewish. For your boyfriend, (whose noble profession implies that while it is a point of intrigue, he is not interested in converting!) – is certainly not Jewish by traditional standards, as even the Jewish genetic indicators (which are not determinative anyway) are on the patrilineal (father’s) side.
By these standards, if you are of Jewish matrilineal descent, then your son, born to you, is Jewish; it is that simple. I hope that this sheds some light on what seems like a fascinating ancestry! And of course, should any of you wish to further explore your Jewish identities, finding a rabbi or educator that matches your Jewish interests and approach would only deepen these intergenerational ties. All the best!