Adding the Grim Reaper (the one in your game, not the one that was on the exchange) caused a serious bug where sims would die, but nobody would come to collect them.
As it turns out, "Grim Reaper" is technically an NPC career, much like being a maid, a tattoo artist or a consignment store clerk (if you ask Grim what he does for a living under friendly interactions, it says he is a Grim Reaper). Once you bring him into the household, he quits his job and become unemployed, just like any other NPC. The problem is that when the Grim Reaper quit his job, nobody replaced him. So when sims died, their ghosts would just hang around by their gravestones and do nothing while they waited endlessly for someone to come.
I believe the reason that you can no longer try for a baby with Grim is because he has no default skin tone. His children often end up with jet black skin, because they don't have a default skin tone, either. I have heard of this causing graphics issues in the game, and even file corruption. There used to be numerous copies of Grim in the Exchange, but as far as I know, they were all removed.
