usage - The house of a friend of Bob’s

How do I say (a friend of Bob’s)’s house?

It’s like a double possesive. Bob’s friends are a class of people. Tom, a friend of Bob’s denotes that he is one among Bob’s friends.

Now what if I want to specify the friend’s name is Tom?

Which of these (if any) applies:

1. I went to a friend of Bob’s, Tom’s, house.


2. I went to a friend of Bob’s’, Tom's, house.


3. I went to a friend of Bobs’s, Tom’s, house?

What’s the correct punctuation and such?

Answer

"a friend of Bob's" means "one of Bob's friends". Therefore, you can say

"I've been to Tom's, one of Bob's friends.

/or/

I've been to Tom's, a friend of Bob's.

You can omit the word "house". It's implicit.