Introduction. The need to study and publish a corpus of letters from Russian religious philosophers is a pressing and relevant sourcestudy task, no less important than the publication of the epistolary writings of classical writers. Only in the last thirty years such archival and textual work has become possible. A truly exceptional place in this context is occupied by the letters of Semyon Lyudvigovich Frank to his wife, Tatyana Sergeevna Frank (née Bartseva, 1886–1984), shedding light on the philosopher’s personality, his family, and his creative and educational activities in interwar Europe. Theoretical analysis. These correspondences reveal a “family idea”, a Christian attitude toward marriage built on concepts of family hierarchy, care, support, and love. When signing his next correspondence to Tatyana Sergeyevna, Frank always finds reverent and encouraging words of love, attention, and respect during the difficult times of exile: “I embrace you warmly, my dear and only one. Thank God, we have love, and where there is love, there is God, and God will not abandon us” (February 12, 1926, Paris). Such is the religious significance of marriage from the perspective of a philosopher, husband, and father. Throughout his epistolary writings, we find Frank’s philosophical and everyday reflections on his wife, children, family, “home”, life and death, close relatives, and friends. The “family thought” in his letters includes reminding his children of the old pre-revolutionary Russia and experiencing the homeland as a sacred place. Conclusion. The themes of the correspondence examined are traditional for works of Russian literature of the 19th and early 20th centuries, Russian family novels and drama, and the epistolary writings of Russian writers and philosophers. The letters constitute a unique philosophical and literary monument to the traditional Orthodox family in the Russian diaspora in the 1920s and 1930s.