…all of us have ancestors of every color and creed. Every Palestinian suicide bomber has Jews in his past. Every Sunni Muslim in Iraq is descended from at least one Shiite. And every Klansman’s family has African roots.

And vice versa.
In Ireland we could add that every Unionist is related to a Nationalist – and so on. It’s one big family squabble, the world over.
And it doesn’t go that far back.

See this fascinating WIRED News article.