Well, I've known Jack for fourteen years.
He's a pretty good friend of mine.
She's known Jack for fourteen years.
He's a pretty good friend of hers.
And I've known Bill for thirteen years. 
He's a pretty good friend of mine.
She's known Bill for thirteen years. 
He's a pretty good friend of hers.
I've known_them_both for quite a long time. 
They're pretty good friends of mine.
She's known them both for quite a long time. 
They're pretty good friends of hers.
I've known Jim for a long time. 
He's an old, old friend of mine.
She's known Jim for a long time 
He's an old, old friend of hers.
We're old friends, old friends. 
He's a dear, old friend of mine.
How long have you known your old friend Sue? 
How long have you known dear Claude and Sue?
Well, I met them just before I met you. 
They're my closest friends, dear Claude and Sue.