Your original post was "Can I use someone else's miles to upgrade my flight?"

As you found out, you can use your Dad's miles, but if it was a non-family member I don't think it would work. Last year I had a client who was going to do that for me and I was told by AA, since he wasn't flying with me, I couldn't use his miles. Someone reading this thread in the future may not realize there could be a problem, depend's on who the "someone" is.