@tianwaifeixian , I would strongly suggest ( for the example you have provided ) that you recognize all three gifts. I say this because (a) there is tax consequence for you and (b) looking at what the law is trying to do is to extend the umbrella over cases where the donor is trying to avoid recognition by parceling out the gift source ( artificially ) amongst related persons and/or trusts/estate etc. Just do the right thing and recognize all the gifts -- it shows an intent to follow the spirit of the law.
At the same time just following the letter of the law ( and not the spirit ) you have to report ONLY person A and B because you know they are related ( and therefore require aggregation ) while C does not have to be recognized.
That is my view .
Hope this helps.
