Brexit has had a big impact on the united Ireland question. It definitely won’t be simple but more and more people are seeing a chance for a united Ireland in their lifetime. Of course Northern Ireland Unionists and Protestants who consider themselves British are hugely against the idea of a United Ireland. And there are lots of Catholics in Northern and the Republic of Ireland who have their own reservations, not least due to the financial cost of a union. But when you know that 56% of the Northern Irish voted to stay in the European Union, you can see why Brexit has affected them hard.
Demographics have shifted as well as the Brexit effect. A century ago when British negotiators carved Northern Ireland from the newly independent south it was 65% Protestant, 35% Catholic, which allowed for a strong unionist majority. Now, a century later it is 48% Protestant and 45% Catholic. When this trend continues, you will see a Catholic majority in 20 years time. How things have shifted since the Troubles 1968-1998.