Some links for now, to reviews of a recently published biography of Proust's mother Jeanne Proust née Weil.
A long essay in The New Republic argues against the idea that Proust was a "Jewish writer" but then agrees that this knowledge of his family background did help him in getting a perspective from the margins which was essential to his aims:
Proust, as we have seen, definitely did not think of himself as a Jew, and neither should we. In his novel, he chooses to represent the maternal side of the narrator's family as Catholic, which corresponds to his choice of making the narrator heterosexual -- two related maneuvers intended to situate the main story in the majority culture. And he abundantly draws on the imagery of the Catholic church, which clearly speaks to his sensibility. Yet all those hours of his formative years in the capacious bosom of the Weil family were not lost on him. For a writer so acute about discriminating social behavior and the multifarious ways in which social norms shaped individual character, the Weils and their many Jewish friends presented to him a fascinating social alternative within the dominant framework of French society.
What is discomfiting to the social consciousness of the individual can be a resource for the artist. Proust's epic project involved creating an elaborate set of finely nuanced yet indelible images of men and women as social animals, responding to the dictates of their milieu, powerfully motivated and often woefully misguided by the horizon of social expectations that defined their world. This synoptic view of the realm of society required fine discriminations between the behavior of different classes and groups. Proust from childhood had known an affluent Parisian milieu that replicated the manners and habits of the general French milieu of the same class and economic standing and yet retained certain differential traits. It seems plausible that his consciousness of this sub-group sharpened his awareness in his effort to define society's kaleidoscope of shifting codes and practices. This familiarity with the residually Jewish world of the Weils afforded him a perspective more socially specific than that of the vague notion of marginality that is often associated with him. Madame Proust's social legacy to her son was not to pass on to him her ancestral heritage, but, through the sheer vibrant presence of her family, to impart to him a doubleness of perception that helped to make him a shrewd and searching chronicler of French society.
More essays from Literary Review and London Review of Books. Elisabeth Ladenson who wrote the LRB review has written a book titled "Proust's Lesbianism" - Now that's one book I want to lay my hands on. Also intriguing because she didn't title it "Proust's Lesbians"...
Publisher's Page has a sample chapter from the biography.