Although “mysl′ semejnaja” may be the dominant idea of Anna Karenina, unhappy families interest Tolstoj the most. Among approximately thirty families described or briefly mentioned in the novel, only two may be called truly “happy” and the number of pages devoted to them is minimal. However, these two give the reader an idea of Tolstoj’s moral hierarchy of families. Anna Karenina is in many ways the author’s expanded meditation on the reasons of happiness or unhappiness. The present paper argues against Sydney Schultze’s definition of a happy family and asserts five main principles according to which families can be structured. One of the cornerstones of family happiness is fidelity to one’s spouse. One of the main plot developments in Anna Karenina is the development of Anna’s family from “rather good” to the actual absence of family, and this development happens because she is unfaithful to her husband. Another very important criterion is a person’s ancestors, that is, pedigree. These two categories, however, seem to overlap: infidelity ruins the purity of pedigree, which plays a key role in Tolstoj’s concept of the family. Tolstoj adheres to the idea “the parents—the children” for an individual’s character is determined and defined by his or her origins. The criterion of ancestors intersects with another one, descendants. Tolstoj’s understanding of the role of children is quite clear: a child is “the moral compass” that shows adults the “true path.” A fourth criterion is role-distribution, i.e., male-female relationships. In the novel, “right” or “wrong” roles are based on the opposition “functionality” vs. “beauty” for females and “fatherhood” vs. “individualism” for males. Place of residence, the fifth principle, overlaps with the second, pedigree.