Yes, please do. I have no doubt Robert Roy was the son of Isabella Roy, and Isabella married James Brand in 1856. In 1861 she had children William Roy (9) and James Brand (3); Robert Roy is not on the census. Anywhere.
Robert is definitely the son of Isabella Brand, due to the matching of signatures.
And in 1871 he married Jane Wedderspoon - unfortunately no signatures on the record. But my grandfather's birth record shows he was a Roy-Wedderspoon product; image attached.
There was as noted a William Roy; but he was 9 at the 1861 census, and Robert would have been 11. I am strongly suspecting Robert was also illegitimate.