My younger brother came back home in these holidays and he seems to have something on his mind. As I expected, he is thinking to quit current job and take over my dad's company in the near future. Previously, he is saying that he doesn't keep on working for current company until he retire. So this is the reasonable thing to happen.
He is worrying about how he can tell his boss about quitting the job and taking over dad's company. In this case, I believe there is nothing to worry about. I've experienced the same event before. Actually, I also quit the job and came back to my hometown for my dad's company a few years ago. Same situation of my brother. My past boss understood my situation and accept my proposal, it means quit the job.
However, I had some problem about the relationship with my dad, president. Eventually, I gave up to work with my dad and quit the job again... And now, fortunately, I entered the local company and work as an engineer.
I can't say to him that "right now quit the job and come back" or "change your mind and keep on working at there". It depends on him. He should decide what to do. All I can say to him is that to consider to put his life, his future first. We all need to think for what we are working. For dad? family? or myself?