I suggest you watch Winter On Fire on Netflix about the 2013 revolution in Kiev. It’s not quite so simple.
Just out of curiosity, to test your theory, Jews and Arabs are cousins. Our languages, customs and thinking are very similar. So why have we been killing each other for the past century on a regular basis?
Sometimes cousins do get lethal. Canada and the US did in 1812. North and South states went at it pretty bad in 1861, as did the Missouri Bushwhackers, which included Frank and Jesse James and their cousins the Youngers, and Kansas Jayhawkers, among whom was John Brown. There is no known kinship between the Hatfields and the McCoys, however. But they still went at it for about forty years.
Fair enough. I suppose I could shoot Antifa scumbags and still get a good night's rest even though they look just like I do (minus the tats, purple hair, and piercings).