With the aim of serving as an academic and professional guide, this work sought to clarify absolutely relevant points about inheritance law between spouses, addressing the property regimes provided for in current civil legislation and emphasising the conventional separation regime. This research was motivated by the great legal debate that exists on the subject. The subject has gained relevance due to the decision of the STJ in REsp 992.749-MS, which stated that a surviving spouse married under this property regime is not an heir when in competition with descendants, which was overturned in the judgement of REsp 1.472.945/RJ, which concluded in absolutely the opposite direction. Thus, in the face of absolutely opposite conclusions by the highest court that regulates Brazilian infra-constitutional law, legal uncertainty on the subject is an incontrovertible point, the discussion of which is the subject of this book.