Sinn Féin for nine years. (It merged with two other organisations to form Fine Gael in 1933.) Anti-Treaty Sinn Féin members continued to boycott the Dáil. At a special "Ard Fheis" in March 1926, de Valera proposed that elected members be allowed to take their seats in the Dáil if and when the controversial Oath of Allegiance was removed. When his motion was defeated, de Valera resigned from Sinn Féin; on 16 May 1926, he founded his own party, Fianna Fáil, which was dedicated to republicanising the Free State from within its political structures. He took most Sinn Féin TDs with him.
Sinéad de Valera and Terence (Terry), and two daughters, Máirín and Emer. On 9 February 1936, Brian, then aged twenty, was killed in a riding accident in the Phoenix Park. Due to a combination of his imprisonment, political activities, and fundraising tours of the United States, the family saw relatively little of Éamon de Valera in the 1916-23 period. He was also away from home frequently during the early years of his political career. Sinéad de Valera played little or no public role during her husband's fifty years in public life. Sinéad de Valera wrote thirty one books for children in both English