As I understand it, if X and Y independently have the same friend Z, we should write Z is a friend of X's and Y's but if X and Y collectively have Z as a friend (e.g., X and Y are a couple), ...
A picture of the king. A picture of the king's. What exactly is the difference between the two?
As this NGram shows, we nearly always use the possessive form of personal pronouns for friend of mine/his/ours/etc. But when it comes to actual names, we prefer friend of Peter without the possessive ...
He's a friend of mine. That's a car of his. Why do we use the possessive when the meaning would be the same while not using it (e.g. a friend of me and a car of him)? I thought maybe it is ...
Think of the simple phrase "Bill's friend". If you were going to turn this around using the preposition 'of' would you say: A friend of Bill's or A friend of Bill It appears to me that, in the US ...