The photo of this gravestone was provided by Jane Leahy and marked by her as being that of Ciss Quinlisk after her visit with PJ and it seems likely he showed her the grave as being that of his aunt and her husband, but this is not certain and needs to be confirmed. The Michael mentioned does not fit as they did not have a child by this name so far as I know.
_Patrick Joseph O'BRIEN ___________ | (1900 - 1979) m 1932 _Thomas Francis O'BRIEN _| | (1936 - ....) m 1956 | | |_Catherine Mary Aloysius QUINLISK _+ | (1900 - 1960) m 1932 | |--Sean O'BRIEN | | ___________________________________ | | |_Maria CALLANAN _________| (1935 - ....) m 1956 | |___________________________________