Dear Mary: Is my brother being gaslighted by his boss?

Q. My brilliant brother, who graduated last year, could find nowhere to live in London so we were all delighted when he found work as a live-in assistant to an interesting (and successful) employer who works from home. My brother is super-efficient and lovely to have around and I’ve no doubt that he’s made himself invaluable, but I am worried that at the same time he seems to be losing his own self-confidence outside of the job.