When Does Responsibility End........

I've been pushed into a situation, I don't want to be in and I'm getting very tired of it..............what I want to know is where does the responsibility end? This person's family dropped him like a hot potato, and left him for me to take care of..........we're not married, he has lived here for 2 years. I am having a hard time dealing with this...........and no help or end is in sight..............I can't drop him at a shelter, because he needs around the clock attention............a stroke victim, is hard to handle.....plus he has diabetes............to boot.........I'm very tired.....of the stress.....