family skeleton

A sinister or scandalous secret that is kept closely guarded by one's family. Typically used in plural constructions. There are some conspiracy theories flying around that the reporter stumbled upon one of the aristocrats' dark family skeletons, prompting them to have her killed. The explosive memoir by the famous actor details all sorts of family skeletons that have been buried for years, including patterns of emotional abuse inflicted by his parents. Even the most seemingly perfect people have some pretty shocking family skeletons.