Three sons of George III of the UK and Hanover succeeded each other on the Hanoverian throne:
Georg IV, Wilhelm IV, Ernst August I.
Some more English examples from the Anglo-Saxon period:
House of Wessex (precursor to the English kings):
Ethelred I 866-871
Alfred the Great 871-899
(All sons of Ethelwulf, King of Wessex 839-858)
House of Wessex (kings of all England):
Edmund I 939-946
(All sons of Edward the Elder, first King of the English 899-924)
The most I could find were 3 siblings. Are there any 4 or plus cases ?
Are there any other cases of 3 siblings ?
Louis X, Philip V, Charles IV
François II, Charles IX, Henri III
Louis XVI, Louis XVIII, Charles X
Luis I, Fernando VI, Carlos III (2 full brothers and a half-brother on his father's side)
Carlo Emanuele IV, Vittorio Emanuele I, Carlo Felice
Erik IV, Abel, Christopher
Edward VI, Mary I; Elizabeth I (3 half siblings just on their father's side)
George II, Alexander, Pavlos