Possibly when you tell him a potentially embarrassing story in the first place, you could say, “please don't repeat this,” so that he'll have an idea from the get-go this is meant to be a private discussion between the two of you. If that doesn't work, you may have to be more selective in what you share with him.
Ask an etiquette question and get an answer from several perspectives: Callie Gordon is 20-something; Lillie-Beth Brinkman is in her 40s; and social columnist Helen Ford Wallace is 60-plus. You'll also find a guest answer. To ask an etiquette question, email firstname.lastname@example.org. For more 20-40-60 etiquette, go to blog.newsok.com/partiesextra.