Thank you both, Elwyn and Shane, for your insight into my problem of not only Hugh Boyle and Mary Ann O'Neill but that also of Hugh Boyle and Susan McQuade. I have tried for years to discover anything I can about my great grandmother, Mary Ann, to no avail. As for Susan, I have searched the civil indexes for a marriage to Hugh from 1872 to 1876. And tried other resources for 1877 including all the Pilot, Rootsweb, Family search and Scotlandpeople with no results.
I start with 1872 because I find Susan still married to John McQuade evidentally, as a baby, Susanna, was born to them on Nov 7, Scotstown. And I end in 1877 because Susan dies March 10 in Glasgow. It's a relatively small window to search but even so, I have found nothing. Susan's maiden name was Reilly, her father, John Reilly.
You may be wondering if she and Hugh really married. All I can say to that is that she is listed as his 2nd wife, deceased, on his death cert in 1900 and he is also listed as the widower of Mary Ann O'Neill and Susan McQuade when he marries his 3rd wife, Sarah (Brannan) McKenna/McCanna in June 1877 in Glasgow. And believe it or not, Sarah dies before Hugh and so he is a widower 3 times! Amazing.
I hope both of you are having great Irish luck with your searches.
Sincere thanks, Finnigan