This article examines a particular aspect of invoking succession unworthiness. Regarding the sphere of persons who would have active procedural capacity in an action to ascertain/stating the indignity, we include in this category: legal or testamentary co-heirs (whose inheritance rights would have been restricted by the coming of the unworthy to inherit); subsequent legal heirs (whom the presence of the unworthy would have removed from the inheritance); donees or legatees (whose liberalities could have been reduced if they had infringed the succession reserve quota of the unworthy); the creditors of the legal co-heirs, of the subsequent legal heirs, of the donees or legatees (the exercise of the oblique action is allowed, not being an exclusive personal right); the unworthy heir. However, there are some dilemmas regarding unworthy heir. Until we can discern a different regime of invocation depending on the type of indignity, legal or judicial, we must answer the fundamental question of its interest. Could the principle nemo auditur turpitudinem allegans be applied in this case? Before finding a definitive answer to this question, this article aims to determine the legal nature of this institution and its history.