My Friend's Brother Seems To Avoid Family. Example: At Thanksgiving

My friend's brother seems to avoid family. Example: At Thanksgiving he arrived, ate, went outside to smoke, got in his car and left. Didn't say anything to anyone. This happens frequently. His mother is hurt by this. Father passes away a few years ago. Has 1 sister, 2 brothers. He does drink alcohol daily. In denial of alcoholism. Would this be an underlying factor for his behavior?