i want a setup where if i rotate A or C, the B feather will stay in between.
Make sure that the bones’ axes are all normal to the line of the wing and pointing in the same direction, then use a driver for bones B & C with bone A as the target. That way when you rotate A the others will follow. You can make B and C rotate more that A so the feathers spread out by making your driver expression something like var • 1.2 for B and var • 1.4 for C where var is the rotation of A. Don’t forget to check Autorun Python Scrpits in User Prefs or your expressions will not work.
PS this is not the best way to achieve what you want. The best method is to use a curve to hold the feathers, put some “hooks” on it to bend it, then ALL the feathers can be smoothly animated. I am not at home near my Mac till next week, so I can’t do any mockup of this system just now. So if you can wait a week I will be able to help further.