The wife of Lenin; Nadezhda Konstantinovna Krupskaya (who is better known as Nadya Krupskaya) has long been asserted to have been jewish. A representative example of this can be found in Frank Britton's 1950 'Behind Communism' where he writes that Krupskaya was 'Lenin's Jewish wife'. (1)
Ironically while Lenin was originally believed to not be jewish (and it turned out his maternal grandfather was) (2) Krupskaya was claimed to be jewish from the get-go by anti-communist authors and authorities. Indeed so ubiquitous is the claim that I believed it until I decided to look into her ancestry a bit in the interests of intellectual rigour.
Krupskaya's jewishness is usually located in her mother's family given that her father was a Russian nobleman of the Krupski genus, which had strong royal connections to the old Polish monarchy (3) and although we know of jewish members of this genus: (4) there is no evidence that her father was one of them (especially as this would have made him suspect in the Russian Imperial Army in which he was an artillery officer). (5)
Krupskaya's mother Elizaveta Vasilyevna Tistrova (who died in Bern in March 1915 not in 1903 as Wikipedia claims) (6) was from a family of landless nobles. (7) I can find no mention of Tistrova being jewish or having any jewish connections what-so-ever: we do rather obscurely know however that she wrote children's poetry (8) and served as housemaid and servant for Lenin and her daughter Nadya. (9)
No jewishness there as far as I can see: indeed, we even know that Krupskaya actually defended people accused of anti-Semitism (which was a crime in the USSR) when she had little reason to do so, (10) which is, I would argue, something we would more closely associate with non-jews than with jews.
The simple fact is that despite the frequent repetition of the claim: there is no reason or evidence I can see for arguing that Krupskaya was jewish or had any identifiable jewish ancestors.
References
(1) Frank Britton, 1950, 'Behind Communism', 1st Edition, Sons of Liberty: Los Angeles, p. 35
(2) On this please see: https://karlradl14.substack.com/p/was-moshko-blank-anti-semitic
(3) Norma Noonan, 2006, 'Nadezha Krupskaia', p. 269 in Francisca de Haan, Krassimira Daskalova, Anna Loutfi (Eds.), 2006, 'A Biographical Dictionary of Women's Movements and Feminisms: Central, Eastern and South Eastern Europe, 19th and 20th Centuries', 1st Edition, Central European University Press: New York
(4) http://kehilalinks.jewishgen.org/kobylnik/a_short_history_of_kobylnik.htm
(5) Helen Rappaport, 2001, 'Encyclopaedia of Women Social Reformers', Vol. I, 1st Edition, ABC-Clio: Santa Barbara, p. 374
(6) Robert Service, 2010, [2000], 'Lenin: A Biography', 1st Edition, Pan: London, p. 229
(7) Noonan, Op. Cit., p. 269
(8) Ibid.
(9) Helen Rappaport, 2009, 'Conspirator: Lenin in Exile', 1st Edition, Hutchinson: London, pp. 16-17
(10) http://www.jta.org/1928/08/07/archive/krupskaya-lenins-widow-defends-teacher-accused-of-anti-semitism