How can I stop my 23 year old son fighting continuously with his 14 year old sister?

I am a sole parent of 6 aged 11, 14, 17, 20, 22 and 23. These 2 just don't get on. They are constantly at each other. My 23 year old pays me board even though he is unemployed but thinks this is his ticket to laziness. He does absolutely nothing around the house and only ever does anything if I threaten to throw him out. He never does any chores of his own free will as all the other children do. I'm at my wits end with his laziness and his constant bickering with his sister. He also swears a lot and swears at his siblings. He is always angry. He is causing eveyone great distress. He is breaking up the harmony of the family. I am a Christian and am trying really hard to put up with him but I'm ready to throw him out!!!