A lot of places expected assassination as a legitimate means of advancement. This is why people used to lock up and blind their own siblings and other relatives. Historically it was a means to advance in armies as well that were in effect rulers. Baibers for example rose to supremacy when his allied leader died in an accident, same with the Huns, Mongols and many others including Europeans. The rule passed through blood line, so everyone had bodyguards and safeguards and the survivors either hid out, were imprisoned or ruled.
Basically at top level it's not murder, rulers have the right to kill, just as governments today do to anyone who challenges their power. Particularly in monarchies, but the Romans had very powerful families where people advanced by killing off their own relatives. Indian dynasties with kings have a lot of kids ended in attempted and successful assassinations in all directions.
It's not murder if they succeed, it's just politics. It's only murder and treason if they fail.
In tyrannies you basically need to slaughter the previous tyrant and then put his crown on with or without washing the blood off it (provided you were happy to put yourself in the firing line of the next ambitious tyrant). Assassination was one way of doing so.
So if you had a society where kids have the birthright to their parents positions then your society can be like this, all elites would have bodyguards from early in life and may the best man win.