Can I add a framing block along a cable to meet stapling code requirements?
I am not very familiar with the term sister, but if it means you're adding a piece of stud to another stud to get closer to your NM for stapling. Then I would say no one would have a problem with that form a code standpoint. Just make sure you're in the center of the wall or at least 1 1/2" from the drywall.