Brother, My Brother

Question: One of my PCs playing a Scion of Amaterasu recently killed his half-brother - admittedly in an attempt to stop him from doing dark deeds. What is the general attitude to kin-slaying amongst the different pantheons, as I can imagine this will pop up again at some point and wondering what opportunities for trouble (I mean development) I can put my players through?

You'd be hard-pressed to find a culture whose myths don't find fratricide pretty much as abhorrent a crime as there is. It's interesting that you're working with the Amatsukami, because they're actually one of the few pantheons that doesn't have an immediate and incredibly violent response to kin-slaying - or, at least, not necessarily to the extreme that other pantheons do. It's still definitely, definitely not okay - not only murder, but murder of a family member is beyond the pale of social rules for pretty much everybody - but they're not the Dodekatheon.

However, if, like most Scions, your PC is in a band with children of gods from other pantheons, he may have to deal with their extreme reactions (or even their parents'). The Dodekatheon are notoriously harsh when it comes to punishing kin-slayers - murdering a family member (especially a divine one) is likely to gain you the extremely unpleasant attentions of folks like Nemesis or the Furies, not to mention usually involving the extreme censure and disavowal of any Greeks who know about it. Greek mythology usually assigns great calamity, misfortune and eventual destruction to those who murder their families; even if your PC's Greek bandmates are understanding that it had to be done, they may want to give him a wide berth to avoid getting hit by any of the inevitable fallout. The Norse are similarly harsh when it comes to the murder of family members, though, depending on how liberal the Aesir your PC associates with are, he might be able to appease some of them by making an appropriately massive weregild to Amaterasu for the loss of her son (and I doubt she'd argue). Persian culture, especially where it rubs up against the Greek lands, is very disapproving of familicide of any kind, and the Tuatha are likely to be appalled by such an act.

Your PC has all the makings of a tragic hero; he may have done what he did for the good of everyone and it might have been the only choice, but fratricide is right up there with the most unforgivable sins for a lot of pantheons. He's likely to find himself dogged by that stigma for a very long time if not forever; depending on his personality, he may try to provide restitution to the family to try to smooth things over, perform some prescribed act (or acts) of penance to appease his allies, or just try to continue being the best hero he can be and hope that his valorous deeds eventually outshine the unfortunate necessity of killing his brother. Scions are by definition more modern than their pantheons, so he may find that his band supports him, as they're likely to have seen firsthand what said brother was capable of and to have wanted him out of the picture.

Sometimes you just have to stick to your guns. It may make life hell when dealing with the fratricide-opposed pantheons... but then again, Kane can seriously be a huge dick.