Originally posted by Homie
I thought it was more advanced. I can't believe that Caesar is up there with Bismarck and Xerses. I think what culture you are also effects relations, I usually play a European civ and that explains why I have better relations with Caesar than with Xerses.
Civs basically have two characteristics: aggression (measured on a 1-5 scale), and types of things they tend to produce.
Some civs are programmed to produce more land units (e.g. the Germans), others are programmed to produce more cultural structures (e.g. India), etc. I don't know how great an effect these "production tendencies" actually have.
Caesar's base aggression level is the same as Xerxes' and Bismarck's. But yes, I think you're right; civs from the same culture group do get along better. Therefore, if you frequently play Mediterranean civs, you'll perceive Caesar as being less aggressive on average. However, this has nothing to do with the Romans' aggression level per se.
Note that production tendencies can indirectly influence temperament; if the Germans are set to produce land units more often, then Bismarck will tend to have a larger standing army, which may tempt him to act more aggressively.
But, all other things being equal, Caesar is just as aggressive as Xerxes. It's possible, though, that the Persians are an inherently stronger civ than Rome (what with Immortals and all), so in practice they will probably have more land, a stronger army, and thus they will often be more aggressive.