When I said who was interviewing me, my dad said "Oh, I know one of them, he and I do research in the same thing. He's written stuff for the journal I edit a few times." Knowing this, I could have gone into my interview and said "You know my dad, he does..." or the like, but not once did the interview mention he'd heard of my dad, if he recognised the name (not particularly common), nor would I have said anything either.
Even if you think you might want to go into the same area of research as your interviewer, don't say it. What you think the material is and what they know it to be is likely to be VASTLY different and you'll only fall over yourself. I'd picked up interesting bits of information about fluid mechanics from my dad over the years, but if I'd tried to strike up a conversation about it with my interviewer I'd have crashed and burned.
As it happened, a small thing I mentioned on my personal statement happened to be a random interest of his too, and we got talking about that. Even now, 4 years later and having had him as a Director of Studies he's not mentioned it again, so there's no way I could have found out before hand, it was just luck. Sometimes things happen just from being honest and truthful, don't go in there trying to think you've read up on their prefered material, because they'll tell instantly if you're trying to blag it.