Originally Posted by Terii Senshi
When a character first joins your party (in the World of Balance, or the World
of Ruin), their level is calculated based on the average level of your current
party members. The level for characters is also recalculated at a few other
points in the game as well. When you first start the game with Terra, her
level is always 3.
The new character's level =
Average of all current members' levels (rounded down)
If a character is joining in the WoR, then the new level will never be lower
than their old level.
If a character is joining for the first time, then a value is added to the
average party level to determine their new level, as follows for each
character:
Terra : +0
Locke : +2
Cyan : +2
Shadow : +0
Edgar : +2
Sabin : +2
Celes : +0
Strago : +2
Relm : +0
Setzer : +0
Mog : +5
Gau : +2
Gogo : +2
Umaro : +0
Banon : -3
Leo : +5