And not just the Spanish. Portugal's history is similar; in fact, the two countries were united for a while. There's a fellow in my church who is of Portuguese ancestry, and a couple of years ago, he checked his roots and found out he was 7/8 Jewish; the only immediate ancestor who wasn't was the great-grandparent that gave him his family name.
There was a Spanish bishop in the 15th century who, because of criticism of his conversos ancestry compiled a genealogical history of all the noble houses of, I think, Aragon. His conclusion showed that even then there was not a single noble house that did not have at least some converso blood. Even Torquemada had converso ancestors. Indeed, on the arms of my grandmother's mother's family who are from Spain there is an unusual device, a yellow (actually gold) fess (horizontal bar) charged with three 6 pointed molets (they look like Stars of David) and are also yellow. It's unusual because almost never do you see one metal charged on top of another, and even rarer the same metal, in this case gold atop gold. It's almost as if it was not meant to be noticed.