He was the son of Joseph Patrick O'Kane J.P. and Kate O'Kane.
In 1901 the family were living in house 18, Castle Street, Ballycastle. By 1911 the property is known as house 19, Castle Street, Ballycastle, Co. Antrim.
The London Gazette dated 28th June 1916 records P O'Kane as being confirmed in his rank of 2nd Lieutenant.
Lt. O’Kane was serving with 4th Bn. Royal Irish Rifles and was attached to 1st Bn. Royal Irish Rifles when he was killed in action on 21st March 1918 aged 23.
The Belfast News Letter of 25th March 1918 reports: