Juliet
Seniority CAN be difficult.
When FTL came into force, two Captains and one F/O were required for our longer duties. Many Captains had joined from their previous employer at the same time and with similar backgrounds. They had all been S/F/Os who "had come with the aircraft" This was resolved so the Captain whose name was first in the alphabet would be IN COMMAND on the flight away from base, and the other was IN COMMAND for the return flight. (As the only F/O, I just had to remember whose word was LAW !)
As a 400 hour new CPL I had had to Check and Certify that my Employer and Chief Pilot was fit to fly IN COMMAND of the Rapide, which he owned, and for which I held the Type Rating. (Just how long the job would have lasted if I HAD FAILED him ... Is a matter for conjecture.)
LT