(JTA) — PBS’ celebrity genealogy show “Finding Your Roots” has had plenty of Jewish guests — Bernie Sanders, Larry David, Paul Rudd and Scarlett Johansson — and the occasional guest, like Paul Ryan, who learn they have a Jewish ancestor on their family tree.

But back in 2019, during the season five premiere, the most dramatic Jewish story the show has unearthed so far: “Game of Thrones” author George R.R. Martin discovers he’s nearly a quarter Jewish.

Martin, 70, grew up in Bayonne, New Jersey. His mother was part Irish, and his father was half Italian. Martin was very close to his paternal grandmother, Grace, whose Italian husband, Louis, left her and started a new family without a divorce (Grace was a devout Catholic).

Martin believed he was at least a little Italian, genetically, but a test of his genetic makeup revealed he actually has no Italian DNA at all. However, the test also showed that he is 22.4 percent Ashkenazi Jew — about the equivalent of having one Jewish grandparent.

To check their results, researchers located one of Louis’ sons from the second family and tested him. If Louis was George’s grandfather, there should have been a partial match — about 6 percent. But there was none.

A test of Martin’s maternal grandparents showed only Irish ancestry, so the show’s researchers speculated that Louis left Grace after discovering she had an affair with a Jewish man.

All a stunned Martin can say on the show is: “You’ve uprooted my worldview.”