My son never comes out of his room. He sleeps all day and gets up to eat and use the bathroom.?

He showers almost daily. He is 22. He will not go to college and has not held a job since graduation except one that was part-time. I believe he has a social phobia.....is this possible. He gets nervous in crowds and in the mall. He hates to inside places where he thinks people might be staring at him or sizing him up. His Dad is not sympathetic at all and is threatening to kick him out of the house. I am worried about him. His two siblings are also painfully shy. His older sister is on panic/anxiety disorder medicine. His younger sister has cut herself before and she had therapy this year. Her self- esteem is much better. His older sister attended college for a year and a half but her panic disorder got in the way. She also started taking concerta for ADHD. Is all of this hereditary? Why are ALL three of my kids having social problems it seems?