A cross-cultural investigation of lacunae contributes to successful intercultural communication, helping in achieving mutual understanding between cultures and solving communication problems between different nations. This study is aimed at identifying and classifying lexical lacunae in the kinship terminologies of the Russian and Kazakh languages. The comparative study reveals semantic, cultural, psychological, evaluative, and aesthetic factors. The material of the study comprises the terms of kinship, selected by the method of continuous sampling from lexicographic sources of the Kazakh and Russian languages, with a total volume of 300 units. Interlanguage lacunae were described from the perspective of comparative structural-semantic analysis. The analysis of kinship terms in the Russian and Kazakh languages showed that there are more similarities than previously thought. Significant differences in Russian and Kazakh kinship terminology were manifested in connection with the allocation of the seme "gender correlation", i.e., the name depends on the gender of the person concerning whom it was used, as well as the seme "age concerning the speaking person". Analysis of Kazakh kinship terms that act as lacunae in the Russian language and their classification in terms of semantics, structure, etymology and cultural components was not considered an object of research until now.