The main aim of this paper is to analyse historical development of mandatory family protection in Roman law of inheritance, the need to develop the mentioned institute, investigate its development along with other branches of Roman inheritance law and to explore the similarities and differences between Roman and contemporary Croatian compulsory inheritance law. As Roman law represents the primary basis for the emergence of the mentioned branch of inheritance law, as well as for continental European law in general, the first part of the paper elaborates, through Roman historical legal periods, an overview of the development and further evolution of the institute of mandatory family protection with the most important influences of both intestate and testamentary inheritance law. The central part of the paper provides a thorough analysis of the institute of Roman mandatory family protection, comparing formal and material compulsory inheritance law and highlighting the importance of Justinian's influence on its further development. Legal remedies by which necessary heir has the right to protect himself and his compulsory portion in case of its violation, their limitations and time limits in which the necessary heir has the right to file a lawsuit are also analysed in depth. Paper concludes with the analysis of the mandatory family protection in Croatian inheritance law, emphasizing similarities with Roman law, as well as differences in legal regulations that indicate how much changes this institute has undergone from ancient times to the present day.