In the modern Irish political beginning, there was the ‘old’ Sinn Féin, the party founded by Arthur Griffith in 1905, from which Eamon De Valera and Michael Collins emerged.
James Connolly’s Labour followed in 1912, while the policies pursued by John Redmond and the Irish Parliamentary Party at Westminster were rendered null and void by both The Great War and the Easter Rising.
Then came the Anglo-Irish Treaty, the split within Sinn Féin, the death of Griffith, the murder of Collins, the Free State-sanctioned executions (later to deny Waterfordian Richard Mulcahy the Taoiseach’s post) and the foundations of Fianna Fáil and Cumann na nGaedheal/Fine Gael.
And from 1922 to the present day, the political thinking sourced to the original Sinn Féin gene pool has dominated Irish politics, while smaller parties (Clann na Poblachta, the Progressive Democrats and, currently at national level, the Greens) have come and gone.
The FF/FG powerbase continues to rule the roost even now, and in all likelihood, both parties will, if the maths so dictate, finally end the Civil War split by forming the next government.