Jeanette - One of the best answers I've seen you write - most likely the best one that I've also answered on.
I'll answer your question AND pose another one to you.
Most of my clients are buyers, so it doesn't come up. Of the sellers I do help, most know what I do and what I present to them. However, most of them do not know what I charge others. Why? Because it's not their business. If I choose to bless a family and lower my fees to help them out of a tight situation, that's my perogative, and frankly, the joys of the job. Some of my most memorable deals are where I made the least amount of money. When people ask me what my commission is (as a seller), I tell them flat out, it varies on what their situation is and what they hope to accomplish. I've had listings as high as 8% (total) and as low as 4% (with 3 going to the buyer's agent).
As for Uncle Joe, he can pay higher, since dear old Ma had me, fed me, raised me and watched over me. Uncle Joe just came over to give me a "knuckle noogie." It's not even a question. I'll work for my Mom for free. Uncle Joe, he gets the family rate.
Now for my question to you, Jeanette.
If acting as a buyer's agent, do you disclose that you are getting more commission from one home over another? Do you clients know that you got more commission on their home over another?
Since buyer agent incentives and commissions vary, it may be even MORE important (keep in mind the seller is paying these all the while) to disclose that to your clients, so that they know that you are unbiased.