This type of behavior was how my family operated. No one ever confronted the person they were upset with directly, it was always done through a third party. A fairly messed-up way to operate. My mom would come and tell me that Dad was upset with me. The expectation was that I would go and apologize to Dad, whether I felt the apology was necessary or not. Or Dad would come to me and tell me how upset he was that Oldest Brother borrowed the car without permission, and expect me to go to Oldest Brother and tell him this, at which point, Oldest Brother was expected to go to Dad and apologize. The underlying rule was that you didn't upset other members of the family. Even if they did something that really upset you and that any normal person would understand why you were upset. Keeping the peace in the family overrode everything else.
And, as the family scapegoat, it was always my fault.
Somewhere in my early 20s, I realized just how messed up this whole operating system was. So I simply refused to play the game anymore.
If someone came to me and told me Mom was upset with me, my reply was, "Well, if Mom wants to talk about it, I'm willing to discuss it with her." If someone came to me with a tale of woe about the behavior of another family member, expecting me to rush to that person and relay the message, I'd reply with "Gee, sounds like you need to discuss this with Dad/Mom/Brother/Sissy."
There were some stunned looks at first, but after about 6 months, people left me out of their little game playing. The whole mess still continued, and to some degree still continues, but I am left out of it, and that's the best outcome I could hope for.