I have read a thread here about the proper usage of who and whom. People are usually confused when to use who and when to use whom. The only thing that we have to remember is that: who=subject (doer of the action) while whom=object (receiver of the action).
WHO: The man who is wearing brown shirt is my father. (the man is the one doing the action (wearing) therefor who should be used)
WHOM: The man whom I was talking with is my father. (take note that the subject is I (doing the action which is talking) and the receiver of the action is the man therefor whom should be used because the man is the object)
I hope this helps. It's the easiest way to remember the use of who and whom as I have learned, so far.
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