If the slayers weren't in any way related, how does killing them all end the slayer line?

I'm watching old Buffy episodes on Netflix, and this has been bugging me. How can The First end the slayer line by having the Bringers kill all the slayers when they aren't even related to each other? And did I miss something about why Buffy or any other slayer is chosen?

I know it's just a show, so don't bother answering if that's going to be it. It's just a bit of TV trivia I want to know.

Dream2013-01-19T19:43:29Z

Favorite Answer

If there were no potential slayers left then the Slayer line couldn't be passed onto anyone else from Faith. The girls don't need to be related to each other, they just need to have the potential to be a Slayer (although it was never really defined what determines this quality.)

The First wanted the bringers to kill all the slayers in training, their watchers and therefore erase their methods too. The First was then planning to kill Faith and then Buffy and then the Slayer line would just fizzle out because there would be no one left alive to pass the essence of the Slayer along to. They explained it in Dirty Girls.

*Spoiler*: However, in Chosen we see a multitude of girls of all ages becoming Slayers, so clearly the First wasn't even close to actually achieving its goal. I love the show so much but there were so many continuity problems in season 7 though that I think it's best to suspend disbelief for a lot of episodes in this season.

FemaleLotRfan2013-01-19T19:40:24Z

Because when a slayer dies another is called (the next slayer is one of thousands of potentials) so the line is just a mystical blood line.
I think the slayer is picked based on strength and if she is ready to be called