He may have been the son of Francis and Mrs Minnie O’Reilly. In 1911 the family are living in house 4, Bowelk, Anny, Monaghan. Their recorded children on Census day are aged 29, 26 (Edward), 21, 18, [16?], 15, 13, 11 and 8. Whilst P J O’Reilly was not recorded at that address, he would have been aged 16 in 1911 and fitted into the above birth pattern.
The family were of Roman Catholic faith.
The National Archives of Ireland released a copy of O'Reilly's 'informal' will signed on 22nd March 1916. He left the 'whole of his property and effects' to his brother, Edward O'Reilly, Bowelk, Ballybay, Co. Monaghan, Ireland. Edward was the 26 year old (in 1911) quoted above.
Informal Will of P J O'Reilly