Could this be the will of the father in law of the Thomas Mylrea who might have been the father of John Mylrea, bookseller ?

COWIN, Philip 1811 Lonan A 5 0106238

This will, which has already been transcribed and is on Brian Lawson's site, mentions a daughter, Elizabeth, and also a Thomas Mylrea. (The most likely baptism for Elizabeth Cowin in the IGI is 25 March 1780, father Philip Cowin)