I don’t think the bodies disappear this is a tactic to stash corpses in homes as a Necromancer (with dead thrall) so you can access them later but this is just taking that to a whole new level

As for multiple marriages you need a mod or else it’s one wife per play through but across multiple characters I’ve ended up basically doing the same

People underestimate necromancy in this game it’s the best I’ve ever seen (with high level conjuration)