Roman Emperors and the \"King\" title

[Theodosius the Great]

If no one else can think of any other instances of “Rex” being used, he must really have been unique.

The seniority of the Roman civil structure under Constantine and his immediate successors ranked something like this:

1. Augustus/Sebastos
   
2. Caesar
   
3. Patrician (honorary)
   
4. Praetorian Prefect
   
5. Vicarius
   
6. Consul
   

Zosimus actually says Constantine reintroduced and elevated the title of Patrician, though honorary, above that of Praetorian Prefect.

Since Hannibalianus' inheritence was so minimal it seems that a new rank had to be created for him. In his case "Rex" must have ranked between a Praetorian Prefect and a Vicarius. Just my guess. I doubt any of Constantine's designated successors were meant to be equal. It would have been unorthodox since there was always a senior emperor. Then again, his succession plans were also unorthodox! What a mess.

Normally, of course, Rex was used to refer to client or foreign kings.

~Theo