Lord Lovidicus had a fort until fairly recently. That one fell apart pretty quickly. Unless he enjoyed living in ruined tunnels with his servants and what he thought would be his wife. Or is the Gray Prince really really old? You'd think he would have noticed something was odd if he had been there quite a long time without aging.
I don't think the Gray Prince is very old.. However, there is really no telling how old Lovidicus might have been, though. Even if it's improbable, there is the possibility that he might have been both vampire and "mad" for a very long time. Maybe the fort fell apart around him as the years went by, while he did nothing about it. Over the years, his servants fled and abandoned him, and it fell apart even more.
However, this still requires a span of quite many years.
Perhaps Lovidicus bought the Fort in it's current state, aiming to restore it.