Re: Sim has multiple deaths and won't die.

The sim I created married him, who was an NPC ingame. He came with Squeamish, Geek and Cat Lover traits. I added Waterproof Sim. I have zero mods installed, so I wouldn't be able to check that. He's only got 2205 available points to spend. I was more focused on her than him for aspirations, so he got left in the dust. I'm hoping by me leaving him in the dust he didnt drink the potion lol!

@jKenassi 

I don't think sims will drink the spellcaster potions autonomously.  I've never had one do it anyway.  So chances are that your sim married one with the hidden immortal trait.  But you can't check for that or do anything about it without a mod.  So that sim will hang around forever.  If you don't care about him, the easiest thing you can do is just delete him in Manage Households.  The downside to doing that is his portrait will disappear from the family tree.

Another thing you can do is move him into his own household by himself and not put him on a lot again.  Make sure that household is not favorited and in the Other Household section in Manage Households and that the sim shows up as Not in World.  The sim will stay in the game and you will probably see him here and there but the portrait will remain intact in your family trees.

Hope this helps.