The aim of this article is to examine the reasons which make an individual threaten other members of the family and the legal effects of such threat. The scope of examination includes selected types of threat in the law of succession and in contract law. The characteristics of threat have been identified and the family members at greatest risk, i.e. the immediate family members have been specified. The following research methods have been used: semiotics, sociological and psychological. The results of the examination lead to the conclusion that it has been increasingly common nowadays to use threat as a means to obtain a certain declaration of will from the next of kin.

Key words: threat, fear, authority, contract law, next of kin.