HAHAHA, yes. A good chunk of of D/C handwaves it away by saying that Jimmy died when Cas was first killed, or makes up some similar explanation. Most don't deal with it at all. That said, it's the ship that got me into the show, so y'know.

WELCOME TO SUPERNATURAL. You got codependent incest, blasphemous dub/non-con, and for a whole season a canon ship was technically necrophilia.