Most successions in one state in a year

Aside from the Year of Four Emperors in antiquity, which state has had the

Hovite...

That was
69 Galba, Otho, Vitellius, Vespasian

but there were six in

238 Maximinus Thrax, Gordian I, Gordian II, Pupienus, Balbinus, Gordian
III

most successive kings, queens, princes, princesses, etc in one calendar
year? I can only really think of the year 1888 for the (only) three German
Emperors: William I, Frederick III and William II.

Hovite...

Any year with a short reign:

Don Aitken...

But some degree of recognition is, and he never got that either,
either as King or even as heir to the throne.

1066 Edward the Confessor, Harold II, William I
1483 Edward IV, Edward V, Ricard III
1553 Edward VI, Jane, Mary I
1936 George V, Edward VIII, George VI

k...

Three popes in 1978.

Alternatively, what has been the lowest ratio of reigns (say, four, five or
more) per a given period of time? For instance, five kings in twelve years
is about two and half years per king.

Charles von Hamm

Hovite...

Egypt, 7th Dynasty, according to Africanus:

"The Seventh Dynasty consisted of seventy kings of Memphis, who reigned
for 70 days."