To mark Presidents Day a few years back I started compiling a list of U.S. Presidents who had been in Brookline before, during, or after their presidency. I identified 7 at first including, of course, John F. Kennedy who was born here in 1917. The list grew with more research and had reached 21 when I last updated it on Presidents Day last year.
This morning, I found a reference to a letter Coolidge wrote to his father in 1908 from the Corey Hill Hospital where he was visiting his step-mother, Carrie Coolidge, while she was treated for an unknown ailment there.
I'll wait until I have more details before adding it to the full list, but there is no doubt that Coolidge makes #22. (In the meantime, you can read about the other 21 presidents in Brookline here.)