Saudi Arabia is a different case because, as in some other Muslim monarchies such as the former Ottoman Empire, the general rule was for the succession to pass to a brother until the entire generation of male relations has expired. Very different than in Christian monarchies were the principle is usually primogeniture and therefore a lateral succession is viewed as the exception rather than the norm.
Since this is the European Royal MB, we are perhaps not supposed to venture outside Europe, but if we do, Saudi Arabia is an obvious example. After the first King, Abdulaziz (Ibn Saud), six of his sons have succeeded each other on the throne: Saud, Faisal, Khalid, Fahd, Abdullah and the present king, Salman. All of them were paternal half-brothers, except Fahd and the current King Salman, who have the same mother. (Of course, the polygamy allowed within Islam complicates matters somewhat...).
If the current line of succession is upheld, King Salman's son, the infamous Crown Prince Mohammad, will succeed his father when he dies, making him the first monarch of the third generation of the Saud dynasty, and the first king since the country's second king, Saud, to succeed his father rather than his brother.
Jane's "statistics" questions made me wonder about bretheren succeeding in a row in the same throne .
I will not consider here all those german houses where all siblings were called to a joint rule but only a normal succession line as in the cases below.
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