Series 9, Family Papers, 1922-1978, is divided into two subseries: Family Correspondence (arranged by correspondent) and Miscellaneous Family Papers (arranged chronologically). The large majority of the family correspondence subseries is the correspondence between Louis and Markoosha, and between both of them and their sons George and Victor and their families. Because Louis and Markoosha lived very separate lives, letters written to them both were often forwarded to each other, or sent in duplicate. Letters from Louis, Markoosha, or one of the children to all family members are filed among the Louis-Markoosha correspondence; letters to or from both sons are kept among George's correspondence. The family papers concern the death of Louis and Markoosha Fischer (including estate papers) and some administrative papers.

The correspondence between Louis and Markoosha before her emigration does not contain letters from Louis apart from one in 1933 (a copy he kept); Markoosha destroyed his letters before she left the Soviet Union. Markoosha's letters for this period are an account of her daily life, the children, her jobs, health, financial situation, and news about their friends in Moscow or Berlin. Markoosha used this correspondence as a reference when she wrote My Lives in Russia. After her and her sons' emigration in 1939, the correspondence between Louis and Markoosha reflected their marital estrangement. As they did not live together, they wrote about themselves, their relationship, their writing, their children, and their financial problems, including Markoosha's need for financial support, which caused many tensions.

The first few years after the family moved to the United States seem to have been overshadowed by Markoosha's attempts to come to terms with the state of her marriage and to set up her own life as a writer and lecturer in the shadow of her husband. She lived at the farm they bought in Quakertown, Pennsylvania (next to the Massings), and was visited by Louis and their sons George and Victor, who by September 1942 had both left home. In 1944 Markoosha received her first lecture contract, and Louis sent her advice on how to maximize the publicity for her just-published book. By this time they wrote each other on a daily basis and on quite friendly terms. In addition, Markoosha filed his correspondence and press clippings, and did some typing for him.

Of particular interest is the correspondence from in the years 1948-1952, which Markoosha spent primarily in Europe. During the first year she worked for the IRRC at displaced persons camps in Germany. Part of the correspondence is about the work for the book Thirteen Who Fled, thirteen personal stories of disaffected Russian émigrés. It was a Fischer family project: Louis was the editor, Markoosha the intermediary between him and the subeditor Nikolai Troitsky (Boris Yakovlev), and Victor and his wife Gloria were translators. After this year Markoosha spent time in Italy writing, before returning to the United States in spring 1950. Markoosha's letters are manifold and lively, but Louis wrote very little in this period. He did encourage his wife to write and be creative, rather than to work for the IRRC. However, she did decide to return to work for the IRRC once more, in Paris. After returning to the United States in 1952, Markoosha went through emotional difficulties. She sold the family farm that summer, lived in various places, and came down with health problems, such that in 1954 doctors told her that she should not strain herself in any way. Louis, however, kept encouraging her to write. From 1956 on, their correspondence was strained and soon virtually nonexistent.

There is significant correspondence from George and Victor Fischer and their families to their parents, especially Markoosha. Of special interest is the correspondence of the boys' years in the Army, where George became a captain and was sent to Europe, presumably because of his knowledge of Russian. The correspondence documents their subsequent careers and family lives. Victor married Gloria Rubinstein while in the Army in 1944, and began a career in town planning and urban development. In 1951 they moved to Alaska where Victor became involved with politics and the movement for Alaskan statehood. Their children Greg, Yonni and Joe were adopted between 1957 and 1959. George followed a career in Russian studies and political science, and became professor at Brandeis, Cornell, Columbia and City University of New York. He married twice: Kitty Hoag in 1948, and Elinor (Nell) Halsted in 1958. George and Nell had two children, Sara and Mark.

The folders containing other than family correspondence consist primarily of George's correspondence concerning his father's death, papers, and estate. Among the correspondence with non-family members are some letters from Svetlana Allilueva to George after his father's death, 1970-1972.