Thanks to some incredibly talented--and devoted--researchers, the y-DNA for the Katzenellenbogen rabbinical lineage has been established. With the help of several documented patrilineal descendent of the MaHaRam, we may be able to connect others to this extraordinary lineage. Moreover, the authors also assert that their research provides "compelling genetic evidence that the Katzenellenbogen rabbinical lineage was most likely Sephardic in origin."
"The Y-DNA Genetic Signature and Ethnic Origin of the Katzenellenbogen Rabbinical Lineage"
BY JEFFREY MARK PAULL, NEIL ROSENSTEIN AND JEFFREY BRISKMAN
http://www.avotaynuonline.com/2016/03/y-dna-genetic-signature-ethni...
If you read the footnote [42] you'll see
SephardicGen Resources: Consolidated Index of Sephardic Surnames. http://www.sephardicgen.com/ databases/indexSrchFrm.html. Garcia, Marquez, and Romero are very common Iberian surnames, and their listing in this index of Sephardic surnames is not meant to imply that all individuals with these surnames are of converso ancestry.