Could you declare civil war on turn 1?

I didn't do it though I think about it. Is it possible to declare or even attack the other Roman factions on Turn 1? Maybe I am a bit of a meglomaniac, but has anyone done it?

You can't do it unless you mod the starting game file. I've tried this once, giving my Julii faction leader every trait and ancilliary that I could that effects his popular standing. At game start, I immediately got the message that the people loved me enough that I could invade Rome and so did that instead of attacking Segesta as the Senate demanded. ~:)