As another interesting data point, in the early centuries of the Ottoman Empire, the regular succession procedure involved the new sultan killing off his brothers to eliminate any chance of usurpation preemptively

I have the impression that this was relatively common among rulers when it came to succession in general. Almost as common as brothers actually usurping their sibling to claim power. With great power comes great inclination to get more!

Seeing this topic discussed always reminds me of Stardust (the movie or book). The king was outright encouraging his sons to defenestrate each other. He was a little disappointed in them - he had killed all his brothers by this age and didn't think they were living up to his standards.