Curiouser and curiouser.
According to the index at Scotland's People, there were 6 Cowie children with mother's maiden surname Murcar or Murker born in Peterhead
Margaret 1872
Annabella 1875
Jane and Alexander (twins) 1877
Christian Ann 1881
Elizabeth 1884
so there's a gap between 1867 and 1872 when you'd expect there to be at least some older children. So where were Alexander and Jane living in the 1861 and 1871 censuses?
There's a death of a James Murcar Cowie, aged 57, in 1927. Is he one of theirs? Where and when was he born?