I don't have PhD in mathematics. But I do have a master's degree in operations research (actually two of them, one in business and one in industrial engineering) and the advisor (John Pisa) of my master's thesis (Fat-tailed distributions in chance-constrained portfolio models) is listed in their genealogy data base. So I thought I'd take a look how far my linage went.
There's a couple of branches, some of the antecedents had two advisors listed, so there's actually three branches that go back from Pisa. There's some impressive names in the lists. They are listed below. Probably it's not that unusual for somebody in mathematics to be able to trace their linage back through some well-known names.
Waclaw Sierpinski had two advisors and so did Stanislaw Zaremba