My Ph.D. advisor at Berkeley was Raimund Seidel, whose other students include Nina Amenta, Cecilia Aragon, Eddie Grove, and Jim Ruppert. No nieces or nephews yet, as far as I know, but I'm sure we'll see little Niñas (and Niños) coming out of Texas in a few years.
Raimund's advisor was John Gilbert, who (apparently) has not had any other students. John's advisor was Robert Tarjan, whose other students include Monika Henzinger (who introduced Raimund to his wife Martina) and Danny Sleator. My cousins once removed include Rex Dwyer, Lyle McGeogh, and Victor Milenkovic. Karen Daniels is my second cousin. Bob Tarjan's advisor was Robert Floyd, whose other students include Zohar Manna (whose student Tom Henzinger is the husband of my great aunt Monika (incest?)) and Ron Rivest.
Sadly, Bob Floyd passed away September 2001. Bob Floyd didn't have a Ph.D.; he sprang forth fully formed from the primordial academic ooze like the legendary creature who climbed out of the sea to found the Merovingian dynasty back in the 5th century. (No, really. It was called the "Quinotaur".) Well, okay, actually, he got a job in the Stanford computer science department back in the days when you didn't need a Ph.D. (How times have changed!) Raimund once told me he would like to chair Bob Floyd's thesis committee, just to introduce a loop into the family tree. I think that would have been cool.
David Eppstein was my advisor while I was at UC Irvine; no half-siblings yet, but one may be gestating. (Yes, I realize I'm stretching the metaphor.) David's advisor was Zvi Galil, who's had at least six other students, but as far as I know, I have no half-cousins. Zvi Galil's advisor was John Hopcroft, whose many other students include Al Aho, Chandrajit Bajaj, Richard Cole, Paul Dietz, Cynthia Dwork, Steve Fortune, and Merrick Furst. Lyle McGeogh was the student of both Danny Sleator and Merrick Furst, so he is actually both my cousin once removed and my half-cousin once removed! John Hopcroft's advisor was R. L. Matson, whose other students (if any) and advisor (if any) are forgotten.
Most of this information was derived from the SIGACT theoretical computer science genealogy, which is unfortunately about two years out of date.
Oh, right. I don't have any descendants yet.