Gordon, thank you for your brilliant suggestion. I was able to locate a PDF copy of the "Fasti" online this morning and located the biographical profile of the Rev. JOHN KERR in Volume 1. It indeed included the names of his parents (DAVID K. KERR and MARY BELL), his wife's parents (JOHN GROVES and MARTHA MARY BAXTER), and even the middle names and exact birthdates of most of his children (which even me Mum didn't know!).
I will next try to obtain a copy of his death certificate from the Scotlandspeople website, which may provide still more details. Now it's on to another generation (David Kerr and Mary Bell; John Groves and Martha Baxter)!
I know that he and Maria were married in Lewisham, but the records office cannot (or WILL not) locate the marriage certificate without knowing the parish in which they were married, so that is yet another quest!