Bullshit. That's just citing adverse possession (i.e., squatter's rights). It wouldn't hold up because he was there by permission.
Easiest thing to do: have her sell it to you (I'm assuming you're a decent relative) for, like, a dollar, alter the deed, and then revert the rights. Or pull a gun on him and order his ass out of the house for eternity. Or fill the basement with concrete while he's asleep. These are but a few things that can be done that would get the desired effect.