Whereas, I am a big proponent of doing anything in the world for one's children, I would not be if taken advantage off. It is not alright for you to be paying most of the bills --- everyone in the household who is working should pay bills. The 20 year old if she is not in college should also contribute. They are certainly taking advantage of you.Give them notice so that they can find a place --- one month --- and if they don't move out I would take legal action.
I see that you are offline. I'll check back later to see if you are back in chat mode.