It is analyzed in this paper the development of the law of intestacy in Roman law, from the Law of the Twelve Tables (451-450 BC), through praetorian and imperial law, to the reforms of Emperor Justinian (527-565 AD), and according to the stages of general development of Roman lawmaking, with accompanying chapters on the right to the debita portio of certain heirs as a reflection of the rights on intestacy. After that, a review of the regulation of the law of intestacy in contemporary Croatian law will be given, also with an analysis of the relevant provisions on the right to the debita portio. The concentration of power and property in the hands of the pater familias during his lifetime, as a Roman citizen with all the rights and obligations and considered as the primary subject of legal relations by most of the legal norms, also made the moment of his death extremely important. Much consideration has therefore been devoted to the regulation of property relations mortis causa from the very beginning, in the acts passed in the assemblies, praetorian edicts, works of jurists, imperial constitutions, and finally in Justinian’s codification (and his Novellae) as the culmination of the development of Roman law. Inheritance law has thus been developed in the interaction of different creators and sources of law, and they have reflected changes in social relations at different stages. In addition, it grew out of the basic provisions of the Law of Twelve Tables, in constant counterbalance of two basic principles, the bases of inheritance – the freedom to bequeath by the testator and the protection of his family’s interests through the laws of intestacy. The changes that inheritance law has undergone during Roman legal history clearly indicate the historical evolution of the sources of law and the way it was created, as well as changes in social and above all the family spheres of life – the transition from an exclusively agnatic relationship as the basis of inheritance through the growing appreciation of cognate kinship. By analyzing the law of intestacy, we can follow the process of strengthening the position of children and women, because, as the understanding of the position of certain groups in society has changed throughout history, primarily regarding equality in family relations, their position in inheritance law, expressed through cognate kinship, is equated with those of agnatic relatives, that is, they were increasingly given precedence over agnates. The culmination of this development occurred with Justinian, who finally regulated inheritance law, abolishing the earlier parallelism of civil and praetorian law, and laying the foundations for today’s inheritance law system. This is especially evident in the fact that even today, blood kinship is primarily important for the law of intestacy. Inheritance law as a whole, and thus including law of intestacy, played a very important role in Roman law, and the institutes of inheritance law that emerged and developed within the Roman inheritance law are received in modern legal orders. The same applies to the right to debita portio that originated and developed in Rome due to the need to protect the interests of close family members of the testator. Therefore, for a proper understanding of inheritance law in the Republic of Croatia today, it is useful to see how, on what historical basis and under the influence of which factors inheritance law developed in Rome, while also making it clear to what extent and in what way we are bound by established rules.