Quote:I'll confirm that is actual cannon... I can't remember the episode, but the guys that modified the first Slayer tried to add more demonic essence to Buffy and she killed them all in the dream/astral place. So yeah, Slayers are at least part demon spiritually... or its in their life force.
Of course, if I'm remembering things correctly, the Slayer line was formed by infusing a girl with some demonic essence (at least according to the fanon I've read - can someone confirm this for me?), so you also have the possibility of friendly fire if Doug tries playing this around a Slayer...
If it was genetic then Robin Wood would be more powerful (baring female only rules). I don't know if he was the only offspring of a Slayer, but if the average age was 15-6 then historically I'd say it wasn't.