I recently learned about the fact that Sichuan peppercorns are actually related to citrus, so was looking for where the connection is... As it turns out[1], there is a "citrus family" (Rutaceae[2]) and a citrus genus (Citrus[3], in that family). The Sichuan plant is a member of the family, but not the genus (that would be Zanthoxylum[4]). Confusing!

  [1] https://news.ycombinator.com/item?id=47248319
  [2] https://en.wikipedia.org/wiki/Rutaceae
  [3] https://en.wikipedia.org/wiki/Citrus
  [4] https://en.wikipedia.org/wiki/Zanthoxylum