When we first met the Walder Frey in season 1, Cat was introduced some of his daughters, granddaughters etc. and there were at least a dozen of them introduced, that was just a small fraction of them and didn't even include any of the men. There are plenty of Freys left, even if most(all?) of the named ones are dead, and they're mostly all called Walder or Walda.
Exactly confirming my point. No named characters remain (from the tv show). Ok good stuff.