Frances
Thanks for that - this is more like trying to do four jigsaws with the pieces all mixed up and no boxes!
The Will of Christopher Brew 1629 e156 which you summarised on MNB is indexed as 1628 in MM - I spent my lunch hour on Wednesday looking for it without success. If it has been mis-bundled that could change the sense of the letters.
If the reference to the will of her son is actually a reference to the 1629 will (and it is the Christopher who married (1) Ann Curmine & (2) Mally Kenish )then the "wife of old Christopher Brew" referred to by Cosnahan is the mother of that Christopher (who marries (1) & (2) above).
The Ewan Christian letter seems to suggest that the "wife of old Christopher Brew" referred to by Cosnahan actually marries the father of Thomas Carrally (presumably after the death of Christopher Brew the (very) older).
You can read the letter in (at least) two ways - that Thomas Carrally is born in 1614 or is of majority in 1614 - if Thomas Carrally and the Thomas Charalaugh who died in 1629 are the same person he must have been born in 1600 because he has too many children to be 14.
One of the problems following this is the references to old and young Christopher and trying to work out when they change person.
Carol