Career
Born in Dublin, O'Shea was a captain in the 18th Hussars of the British Army. However, that will was overturned upon appeal, and the aunt's legacy was shared among Katharine O'Shea's siblings. After the divorce the two surviving children of CS Parnell and Katherine O'Shea were given into Captain O'Shea's custody.
O'Shea was MP for Clare from 1880 to 1885 and Galway Borough for a short period in 1886.