Hi Abiam
The 1913 marriage for Joseph sort of throws everything in the air! However, I cannot see see a marriage, surprisingly as they are quite common names, for a John or James Ferguson and a Christina Mor*ison between 1875 - 1895 anywhere in Scotland on SP. I would also say that the names James and John are quite different and not normally interchangeable.
If you are certain of the Morrison middle name for Joseph and that his origins were from Aberdeenshire before a move to Ayrshire, then that 1893 birth cert would look to be the correct one. This then makes the information we have found already for his parents James F and Christina Shea also correct. Their births and family, having confirmed their parents from their marriage certificate in 1893, you already have. This family do look to have moved from Aberdeenshire to Ayrshire just before the 1901 census. A change of occupation for James father from farm servant to police constable in not unusual necessarily. Many police constables would have joined a force from agricultural origins. By 1913 when Joseph married, James looks to have left the Police force and shows as store keeper. Not sure when James may have changed occupations, maybe in Aberdeenshire, maybe the last birth in Aberdeenshire would be good to check. Or it may have come about as part of the family's move to Ayrshire?
There is a death in 1961 in Kilmarnock Ayrshire for a Christina Shee/Ferguson, age 88.
It's a pity when BMDs have conflicting information. Maybe checking the details on Joseph's death cert. might be the next step?
Looking at father James' BC in 1874 I think gives a possible confirmation of birth place that shows on the 1901 census, although still not one that I reconise - hopefully someone else can help on this:
