Probably not much help but can add to the info you're already collecting - that's if you haven't already discovered it - but it would seem the daughter Robina, was named after Mary Black's grandmother, Robina Turnball. 
I've spent some time this afternoon looking around for your 'Wullie' - he certainly is an enigma.  It seems likely he is the one born in Ayrshire, 1860 - have you actually accepted this or still holding out that he could be from elsewhere?