There are in this world of ours many separate fandoms, and sometimes they overlap. Often they overlap fairly predictably. So an Anita Brookner fan is probably also going to be at least some sort of a devotee of Henry James (that's me) or Edith Wharton (not me). Other authors who crop up in this regard include Barbara Pym (a not too enormous yes) and Jane Austen (ditto), writers whose world views perhaps aren't quite so aligned with Brookner's.
But the coincidences I look for are the stranger ones. Who would have thought the fandoms of Anita Brookner and, for example, Doctor Who might converge? But I find more than a few folk. Myself included. There - I trust I've succeeded in surprising you.
I have other enthusiasms. But I have yet to find Brookner fans who are also, say, Kingsley Amis fans or fans of certain 1980s sitcoms. But I live in hope.