I'm no lawyer; but I play one on FR. Wouldn't the disposition of the case depend on whether or not there was a written lease, signed by both parties? If it was merely a verbal agreement, as I suspect it was, it would then seem that the father's stated warning about not bringing porn into the house would also be one of the terms of the "lease."
I’m no lawyer either, but we’re all just throwing our two cents in about this case.
I really don’t know how the court will rule here, but based upon what I’ve read, and other posters’ thoughts, I think the plaintiff may come out on top.
As an earlier poster said, if there are emails between the ex-tenant and the landlords which prove he was told to keep his porn collection off the property, then it’s over. He’s toast.