Answer
Abdulaziz attempted to name his own son as heir to the throne, and this spurned Murad V to participate in his overthrow. Murad V was the nephew of Abdulaziz, and he was next in line to the throne after Abdulaziz's son. However, Abdulaziz decided to name his own son as heir to the throne, which upset Murad V and caused him to join in the conspiracy to overthrow Abdulaziz.