Well according to this Wikipedia article about the Irish Conflict, " A key issue was the
status of Northern Ireland.
Unionists and
loyalists, who for historical reasons were mostly
Ulster Protestants, wanted Northern Ireland to remain within the
United Kingdom.
Irish nationalists and
republicans, who were mostly
Irish Catholics, wanted Northern Ireland to leave the United Kingdom and join a
united Ireland.".
https://en.wikipedia.org/wiki/The_Troubles#Proposal_of_an_independent_Northern_Ireland. So these Irish nationalists and republicans who were mostly Irish Catholics, were they the minority in Northern Ireland then, if you are stating that not even all of the Catholics in Northern Ireland wanted to join The Republic of Ireland?
If so, why didn't those Republic-loving Catholics just leave and go to the Republic of Ireland themselves since they are the minority and leave the rest of Northern Ireland alone? How could they become strong enough to launch almost a civil war? That is ridiculous!!!