family talk

Talk or discussion that is kept entirely within a family for fear that outsiders will find out what is really going on within the family.

"Son, the fact that your mother and I drink heavily is family talk and should never be shared with your grandma and grandpa."

"Son, you should never tell anyone that your mother is addicted to diet pills and enjoys daily doses phenobarbital. You tell anyone about it and I'll beat the hell out of you."