I am coming to this conversation late, but I have good news! Robert Davidson was definitely alive in January 1863, because I have a letter he wrote to his daughter Sarah then, from the ship SS Northam, 'about 2200 miles from Gall (Ceylon). He sounds well and jovial ('is your mother still as fat yet?')
I have a bunch of letters between the Davidson family siblings, mainly to Sarah who was working for a dressmaker in Glasgow. Her mum Agnes disapproves severely of her boyfriend, James Lapraik. Luckily, they ignored her, otherwise I wouldn't be here.
They are all keen on schooling, (Jane is 'top of the class'), Tom works for the doctor stirring the potions. They go to church regularly, enjoy a dance, and play the concertina. Sarah goes to a 'Diorama' in Glasgow, I think it's an early cinema.
I hope some of you may see this (even though it is sadly 8 years after your conversation)