Stick to your guns!! NO BORDERS! My Grandpa got suckered in on a deal like this with a relative and it was a disaster. Just the disruption of sharing his space nearly drove him crazy and then when you added in that his border was a night owl and he is an early bird it was awful.
Be nice about it but don't be bullied into doing what you know in your heart is not right for you. You worked hard. You built a life. It is not your job to provide for every shirt tail relative that knocks on the door.