Robert was living with Allan and Isabella McLean, Mary, Donald and Ann in 1851 in Rothesay. Although recorded as born on Coll in that census all other censuses say he was born at Rothesay. The family moved to Glasgow before 1861. In 1870 Robert married Sarah Graham. The wedding certificate has Robert's parents as Donald McLean and Margaret McLean, maiden name Campbell, witnesses Andrew Alexander and Margaret Hope. Margaret was Sarah's mother, she had remarried after Sarah's father died. I'm not good at reading old handwriting but Margaret's maiden name was something like Fairley.
I have no siblings for Robert and no indication that he ever lived with his mother. Donald was not living with his parents on Coll in 1841 but a Donald McLean was living in Rothesay in the same street as a Margaret Campbell