Thank you Susan- that's fantastic. Sadly, I think my quest to find a living link is gone, as Janet Mackay did not marry and David Mackay had only one daughter who did not marry!!
But it is good to be able to find what happened to them.

I also have found a David Mackay aged 73yrs, widower, naturalised Court of Common Pleases New York, NY 1892, of 2559, 14th Street, Astoria, NY, shown on passenger list for ship arriving back in New York on 19 July 1937, after visiting relatives in Scotland. Thanks again for your help.
Kind regards, Maggie - Australia