coregency
/kɒrɪˈdʒɛnsi/Definitions
1. noun
A system of government in which two or more rulers share power and authority, often used in ancient or monarchic systems.
“During her coregency with her father, she learned valuable skills about ruling a kingdom.”
2. noun
The period of time during which two or more rulers share power and authority.
“The coregency between the emperor and his son lasted for nearly a decade before the son took complete control.”