Ken, thanks for sharing your insight.  This is certainly a plausible theory as to the origin of his Jewish DNA. One thing I know is that his family tradition held that his ancestors in Ireland were called the "Black Irish", which is a term I have found mentioned in commentary on Sephardic Jews of Ireland, though not exclusively. The surname O'Halloran in Gaelic means "stranger from across the sea." However, it is known that O'Hallorans established their clan in Ireland before the Inquisition, and I have not found any evidence that they were of Jewish ancestry. Also, the common Y-DNA haplogroup among Irish males, including ones with O'Halloran/Halloran surname, is the R haplogroup, which doesn't add up with his predicted Q-M378 haplogroup, using MorleyDNA and YFull software at least (I ordered a LivingDNA Y-DNA and mtDNA kit to get a better picture and I'll update this post when I get those results in several weeks). I do think his ~11.5% West Asian DNA (and I should add that although it's not a significant percentage, his report estimated 1.2% Iberian) does hint at Sephardic ancestry in combination with his Ashkenazi ancestry, I'm just doubtful it comes from the O'Hallorans in his family tree considering all the above that's known about Irish O'Hallorans. I think there are 3 plausible theories: a) his grandfather was Jewish and adopted by Irish O'Halloran family, b) his grandfather's mother had an extramarital affair with a Jewish man, or c) all the O'Hallorans and women who married them were Jews who changed their names to be common Irish names and assimilated into Irish Catholicism (they adhered to Catholicism for several generations in his family tree). Gonna keep searching for answers though. Thanks again for your feedback!