I think everyone in this thread is overemphasizing the role that Caligula played in the constitutional and familial history of the Empire. Caligula was only the fourth or fifth son of Germanicus, and was only in a position to take power after Sejanus had all his brothers killed. Furthermore, even when he was the emperor, he didn't do much and he's only made out as an insane monster in hindsight (particularly by senator-historians, who would've hated him anyways). He was really a very marginal member of the Julian family, and wasn't even the sole emperor after the death of Tiberius, but rather he shared the office of princeps with his second cousin (third cousin by blood), Tiberius Gemellus (although he would have Gemellus killed). So its doubtful that Caligula would have any real means to take power over the other sons of Germanicus (or the sons of Gaius for that matter).[/QUOT
I am saying the same thing... Caligula was the fifth son and third surviving of Germanicus, plus he was born much after our POD...
p.s.: Tiberius Gemellus was first and second cousin of Caligula by blood (Germanicus and Drusus Minor were first cousins - their fathers were brothers - and Gemellus' mother was Germanicus' sister) and first cousin by adoption