For Monarchies, Crown Prince/ss, then, if Constitutional Monarchy, Deputy (Vice) Prime Minister or Vice President
For any others, the similar to above.
The Crown Prince to the Forsvarssen throne (Forsvarssen is the ruling family) is Crown Prince Gustav III Forsvarssen
The Vice Prime Minister of the Northern Kingdoms is Makoto Shiomi (native Northern Kingdomer of Zipanguan blood, the first Zipanguan to be Vice Prime Minister)