He seized the lordship by allying with his family's rivals to kill his brother Rory Caoch O'More.

He entered an alliance with Brian O'Connor Faly, the Lord of Offaly - a rival noble who was mistrusted by O'More's father and brother - by marrying his daughter.

As O'Connor Faly's ally, O'More gained the favour of the Lord Deputy of Ireland, Englishman Anthony St Leger.

O'More and O'Connor Faly feared they could lose their patron,[1] and invaded Co. Kildare in late 1546, attacking the Anglo-Irish settlements.

[1] St Leger forced Rory and Giolla Pádraig to submit to authorities, bringing them to Dublin in hopes of stopping their bloodshed.

When the Lord Justice, Anthony St. Leger, had heard of this, he came into Offaly, and plundered and burned the country as far as the Togher of Cruachan; and he remained there two nights, but he returned without receiving battle or submission.

O'More and O'Connor Faly were brought to England and imprisoned in the Marshalsea, a prison in Southwark, London.

[4][5] His death is referenced in the Annals of the Four Masters:"Giolla Pádraig O'More died suddenly in England; and he would have been a lamentable loss, were it not for the power of the English.