I argued with my father! I want PRIVACY!?

The problem is that since christmas is coming, my house will be the place were all family member will have dinner. My dad's identical twin has an 8-year half-paralytic son . That means he has an irregular spinal cord from the middle so he can't move his legs and will be on wheel chair all his life. I've never insulted him in my whole life and my dad told me that he is COMING to stay at our house for a week and when the dinner is over his parents (my aunt and uncle) will pick him up. Everything was fine until he told me that he was going to sleep at my room! I asked my dad why couldn't he sleep at the sofa room and he threatened me that he will punish me if i ever insulted him like that. I NEVER try to insult him, i just like my PRIVACY! We had a lot of discussions and he actually tried to push me to the floor and kick me! I don't want HIM in my room and i told him that if he goes to my room i will leave the house. But i am a 14 year old boy and can't do anything!!