When shooting at someone who is behind someone else, you have a chance to hit the person in front. I've also seen the reverse happening, shooting at the guy in front, missing and hitting the guy in the back.

How does the chance to hit work here? Does a higher chance to hit also increase the chance to hit the guy in front? Is it rolled twice?

If a target is covered by two allies, does that decrease the chance of outright missing? Does shooting at a target who has a shield (and thus higher ranged defense) increase the chance of hitting the other guy?

I'm not relying on hitting targets by missing others but my curiosity was sparked, thanks for any answers!