
thenobledrake |
The rules on this are basically that you can't do this.
In the introduction chapter, where the book explains how to read a rules element, it states that the only feats you can take more than once are the ones that explicitly say you can and what happens when you do.
So if your background and class feature are both giving you the same feat, choose a different background (or a different class feature if that's a choice which isn't always the case).

PawnJJ |
Yeah it would be a dead feat. If it's PFS your only option is to choose a different background.
If it's not PFS and the background fits your character so much that you couldn't imagine it being different, like maybe a Forensic Medicine Investigator with the field medic background, then work with your GM.
Backgrounds are probably the easiest thing to homebrew since they have such clearly defined guidelines.