grammar - Double possessive: a friend of Steven's

I am wondering about the "double possessive" I have been reading about.

I have a couple of sentences as an example:

He’s a new client of Jane and Kevin’s and a close childhood friend of Steven O’Neill’s.

I thought that the above sentence was correct, because it sounds natural to use the apostrophe S to me, in the same way that we say "he's a friend of mine."

However, I have heard people criticize sentences such as that one above as having a "double possessive" because of the OF as well as the apostrophe S.

Is the above sentence correct or should it be:

He’s a new client of Jane and Kevin and a close childhood friend of Steven O’Neill.

Thank you - any help would be greatly appreciated.