A family secret can be defined as "events or information that members hide from each other or those outside the family." Family secrets can be shared by the whole family, by some family members or kept by an individual member of the family. Anecdotally, family secrets may be accepted as a form of preventing others from experiencing unnecessary pain or even maintain a family's reputation. The effects of keeping a family secret can have positive or negative impacts on individuals involved, although it has remained a subject of much debate.

Despite the negative implications and associations of holding a family secret, many believe the act is beneficial and even a necessary function of maintaining familial and interpersonal relationships. The act of with-holding or differentially sharing information is also linked to the setting of boundaries and alliances which underscore the structures of relational systems.

Family members often see keeping the secrets as important to keeping the family working, but over time the secrets can increase the anxiety in the family. The confidentiality of family secrets revealed by a patient is a common ethical dilemma for counsellors and therapists.

According to the early work of Karpel, a typology of secrets emerges through the boundaries created in keeping and sharing family secrets. There are three major types of secrets under the classification:

The concealment of family secrets is partially explained through the communication privacy management theory. The theory argues that people like to conceal information in order to avoid feeling vulnerable and maintain control over their personal information. In a familial settings, managing private information is much more challenging as some members can reveal more than is desired to those considered "outsiders".

The primary reason individuals tend to keep family secrets is protection, linked to associated feelings of vulnerability when disclosing private information. Individuals may aim to protect themselves, their relationships with other family members and even other people.

Familial secrets tend to be concerned with facts as opposed to feelings or thoughts as encompassed under "real happenings or incidents." These secrets can be further categorised into; taboo topics, rule violations and conventional secrets.

Taboo topics are often recognised as secrets on topics that have been stigmatised by society (e.g. addiction, affairs, sexual preference and even divorce). These secrets will often result in negative consequences to a more severe degree than other types of secrets if they are shared.