Lisbon Regicide
The assassination of King Carlos and the Prince Royal was the effective end of a constitutional monarchy in Portugal (later confirmed by the 5 October 1910 revolution). The regime functioned for another 33 months with growing agitation and demands for reform (although considerably less than in the future First Republic). It cannot be denied that the weak and permissive attitude in the Government of Acclamation was an incentive for the Republican Party to attempt another coup. The assassinations did not change the system of government; instead, they delayed the change.
Brazil
With the end of the Peninsular War in 1814, the courts of Europe demanded that Queen Maria I and Prince Regent João return to Portugal, deeming it unfit for the head of an ancient European monarchy to reside in a colony. In 1815, to justify continuing to live in Brazil, where the royal court had thrived for the prior six years, the Crown established the United Kingdom of Portugal, Brazil, and the Algarves, thus creating a pluricontinental transatlantic monarchic state. However, such a ploy didn't last long, since the leadership in Portugal, resentful of the new status of its larger colony, continued to require the return of court to Lisbon (as postulated by the Liberal Revolution of 1820), and also groups of Brazilians, impatient for practical and real changes, still demanded independence and a republic, as demonstrated by the 1817 Pernambucan Revolt.
In 1821, as a demand of revolutionaries who had taken the city of Porto, D. João VI was unable to hold out any longer, and departed for Lisbon. There he swore an oath to the new constitution, leaving his son, Prince Pedro de Alcântara, as Regent of the Kingdom of Brazil.