Shane,
It actually says Chas as fathers first name, Chas/James, could be misheard I suppose.
As to James and Charlotte's children, they had a son also called James Mernagh born 1884 in Birmingham.
He is my husbands great-grandfather, James b1884 had a daughter called Charlotte Mernagh b1914, who then married William Blair in 1938, who in turn had my father-in-law John b1946.
So it is a direct line I am trying to trace, I also cannot get far on the Blair side either, as William disappeared after WW2, and I can't find him or a death record to trace further back through that line.
Angi x