Originally Posted By: BranShea
I dug up the initial post
Originally Posted By: BranShea
Here's a little thing I longtime wanted to ask. You say:

I will be at my sister's.
She's a friend of my sister's.

In the first sentence this seems clearly to mean: "At my sister's " house or place.
The second form always struck me as odd. "a friend of my sister's" ... what?

Maybe I am making mistakes here, but I just would like to know the details about this. (thanks)

I reread the Michael Quinion article from Jim's link and keep on using the double genitive anyway as it's stuck in my head since schooldays. > link

"a friend of my sister" is good.

live in the moment