User blog comment:CoolJazzman/Blood in all the Quincies/@comment-1387259-20130724181034

Well, if you look at Timeline of Events, Yhwach has been around for at least 1,000 years (don't know about 2,000, but it's possible). I'm going with an Adam and Eve theory here. He's the ancestor of all of them, but he didn't necessarily need to have all those children. He could have directly had 3, and a few tens of generations of inbreeding later, you get the modern day Quincies.