He was born in the village of Richhill, County Armagh, the first-born son of the previous head Conn Ó Néill and wife Cecilia O'Hanlon.
In 1740, for religious and political motives, he moved to Portugal with his brothers, where he was an important proprietor in the Council of Almada.
[1][2] He married in Lisbon, São Paulo, on 2 September 1750 to Valentina Maria Josefa Ferreira (Torres Vedras, Carmões, 14 February 1730 - ?
), daughter of José Ferreira (Lisbon, São Miguel de Alfama - ?
), and wife Maria Ferreira (Torres Vedras, Carmões - ?