Taking information from the post "The Start" we have sufficient information to get James and Margaret married.
Facts
From Birth of William in 1877
Name, Surname, & Rank or Profession of Father: (husband)
James Mc Cartney, Colporteur, Byres Kilwinning,
Name and Maiden Surname of Mother: (wife)
Margaret Mc Cartney, M.S, Carley
Date and Place of Marriage:
1876, November 17th, Fairlie 
Additional information obtained from the document above;
Took place in the Free Church of Scotland
Both are 23 years old
His father (William) was a shoemaker and is deceased
His mother (Margaret) maiden surname is Ward still living
Her father (Peter Carley) coal miner
Her mother (Mary) maiden surname was Blain and she is deceased
