MaryJane (McCoubrey) Nelson's Death Registration lists her being 68 when she died in 1920, estimating her birth year as 1852. I found Mary Jane Nelson in the 1901 Census listed as the Head of Household, when my grandfather, Robert, was 6 years old. His father, David Nelson, was not listed in the 1901 Census; However he was listed as Head of Household in the 1911 Census, when my grandfather was 16.
There is a wedding witness, James McCoubrey, listed on their marriage registration. I think he might have been MaryJane's brother but I am not certain, as I have not yet found a definitive records indicating a family relationship. MaryJane and David had 9 children, my grandfather born in 1894, being the youngest. All 8 boy's birth registrations list "McCoubrey" as the mother's maiden name; However, the one girl born in 1880 named Margaret Jane Nelson (later referred to as Maggie) lists the mother's maiden name as "Fitzsimons". It appears that most of the births were registered by a registrar named Dickson and several list the name of an assistant (midwife?), most marked with an "X" whose names I did not recognize. In general, I noticed that most of the Fitzsimons names I researched were listed as Catholic, whereas all the McCoubreys and Nelsons are Protestant. Might this be a factor in some way? Also, I can't find any Death Registrations on James Fitzsimons, but there is one on a James McCoubrey within the correct years. Puzzling. Thanks again for your input.
Age on death registration was generally the least reliable. Best regarded as an estimate. The informant may not have known the person's age. An Irish relative by marriage of mine, born around the same time as your Mary Jane, was inconsistent about her age. I estimated a likely age taking into account when she married, had children and her ages on census. She survived into her late 80's but her son estimated her age as 70-something when he reported her death.
Did Mary Jane Nelson put her status as "married" on 1901 census ? Her husband may have been working away for an extended period, perhaps outside Ireland.
Have you looked for a marriage for James McCoubrey who might have been Mary Jane's brother around the same area? He may have been a cousin or another relative.
The surname prefix Fitz is Norman. Fitz surnames are Anglo-Irish whose settlement of Ireland began in 12th century, 350 years before the Reformation. Some Anglo-Irish remained Catholic after the Reformation, some joined the Church of Ireland during the nearly 300 years post-Reformation when Catholics were dispossessed and discriminated against.
Religious differences may have been a factor in delaying a marriage. I noticed that Fitzsimons and MCCoubrey fathers were both noted as deceased at the time of the marriage, so not able to object to the match.
The wedding was in a Presbyterian church. If James Fitzsimons was Catholic it may have taken some time to agree on whether to marry and where. Marriage law at the time in Ireland differed according to religious denominations of the people getting married. Civil registration of marriages began in 1845 except for marriages in Catholic churches. A marriage in a Catholic church was legal only if both parties were Catholic and had been for the previous 12 months. A few Irish couples of mixed denominations had 2 wedding ceremonies, one in a Catholic church, which had no legal status, and a legal ceremony at another venue. Days, weeks, months or even years might elapse between the 2 ceremonies.
Considering the occupations of James Fitzsimons and Mary McCoubrey, farm labourer and house servant, other reasons to delay marriage, if it was delayed, may have been that James couldn't afford to provide financially for a wife and family and didn't have a home. Both of them may have lodged with their employers. A farmer's son may have delayed marriage until he could take over a tenancy when his parent died or became infirm.
Possible reasons why you can't find a death registration for James Fitzsimons:
He may have died before 1864 when civil registration of deaths began in Ireland.
He may have left Ireland, either for Britain or emigration to e.g. Canada, U.S.A, Australia, New Zealand. Emigration from Ireland was high in 1850's. A man might emigrate first and send for his wife and children when he'd earned enough to pay for their passage.
He may have moved elsewhere in Ireland to work.
Have you found a death registration for James' wife?