Hi all ,
Think Robert's wife was Jane Grant(b. c1827).
Can't see Robert on the 1881 Census , there is a Jane Middleton age 55 showing as widowed.
Scotlandspeople has a Robert Middleton death 1878 St Nicholas Aberdeen , born c1814.
Think Robert and Jane were in St. Nicholas in 1871.
ev
Added - SP has a Jane Middleton(other surname Grant) death 1881 St. Nicholas Aberdeen , born c1827.