Hmmm.
There is only one record of an Alexander born in Kemnay 1867-1871 with mother's name Paterson but he is Alexander Stevenson, born 1 February 1869, parents Alexander Stevenson and Ann Paterson.
Could he have been illegitimate? Or could his mother have been widowed and later have married an Alexander Smith?
Ann Stevenson or Paterson, mother's maiden surname Smith, died in Aberdeen in 1910 aged 64. Could that be relevant?
Alexander Stevenson and Ann Paterson also had a son Burnett George Stevenson, born 1870 in Kemnay, died 1872 in Aberdeen. In 1871 Ann Stevenson, 25, born Keith is in Aberdeen with sons Alexander, 2, and George, 1, both born in Kemnay.
Or is all this a trail of red herrings?