This article presents the results of studying of burghers’ families’ structure in the cities of the Tomsk province of the Russian Empire in the pre-reform period. The author analyzes the structure of middle-class families using common in the demography classification of the family depending on the total number of its members. The analysis of the distribution of families with different types of internal structure shows that among the burghers of Tomsk, Barnaul and Biysk, almost for the entire period of study, the most units constituted extremely simple cell. The author states in the article that a certain share of the bourgeois families accounted for different variants of the extended family, but their indexes declined in the mid 19th century. The paper also presents an analysis of the distribution of families by the number of generations and gives the dynamics of these indicators during the first half of the19th century. The author concludes that during the pre-reform period while retaining the tradition of many-generation family, the family tended to become a one-generation family. The majority of families in Tomsk and Barnaul were two-generation families. In the author’s opinion, it means that the complex and undivided family in the south of Western Siberia tended to disintegrate, segment and simplify their internal and generation structure. The reason for this was not so much the development of the urban market economy, but the influx of population in cities in Siberia.