Hi Pauline
Your family history sums up the joys and frustration of Irish family history research! With the records you have accessed in Scotland, we wish ours were as comprehensive, you have built up a very detailed family tree going back 3 generations. You know, for example, that Patrick Brannan was born in Ireland c. 1857 to parents James Brannan and Isabella McLuskey
Your Irish roots are in no doubt, your problem being that at present you hold no clues as to county or parish of origin of Patrick Brannan. Furthermore, Brannan as an Irish surname originated in a number of different localities within Ireland; in Roscommon as Gaelic
Mac Branáin and in Fermanagh as Gaelic
Ó Branáin. Also, the name has been anglicised as Brennan which strictly speaking is derived from Gaelic
Ó Braonáin which originated in 4 different localities in Ireland in Galway, Kerry, Kilkenny and Westmeath.
Hence Brannan is a surname that is found throughout Ireland, and it is also possible that in a baptism register Patrick’s family name may have been recorded as either Brannan or Brennan.
Prior to 1864 and introduction of civil registration of births in Ireland you will have to rely on church baptismal registers, organised by parish, to confirm the birth place of Patrick Brannan. As you hold no clues as to where in Ireland Patrick was born you will have to rely either on someone in the wider genealogical community knowing more information as to the place of origin of Patrick or to identifying a baptismal record in a database of church registers in the ‘big’ 2 databases of Irish church registers, namely
http://www.irishgenealogy.ie and
http://www.rootsireland.ie.
I did a quick check of RootsIreland and it records no baptismal entries of a Patrick Brannan with father James in the time period 1852-1862. However, it records 33 baptismal records of a Patrick Brennan with father James in time period 1852-1862 but none with a mother’s first name of Isabella.
At time of mid-19th century Griffith’s Valuation it would be reasonable to assume that Patrick’s father, i.e. James Brannan may have been recorded as a head of household. However, the index to Griffith’s Valuation at RootsIreland records 8 households headed by James Brannan and 390 by James Brennan!
Hence it would appear that you need to find a source, whether it is a record or a person with knowledge of the family, that locates the county and, in the ideal world, parish of origin of your Brannan ancestors.