Complex sentence: The heir apparent from 2005 to 2011 was the late Sultan bin Abdulaziz; the second heir apparent was Nayef bin Abdulaziz from 2011 to his death in 2012.
Split into simpler sentences: The heir apparent from 2005 to 2011 was late Sultan bin Abdulaziz. Second heir apparent was Nayef bin Abdulaziz from 2011 to his death in 2012.