I was probably a fairly sensitive child. Playing with friends, just occasionally they would gang up on me - verbally, not physically. I hated it.
My wife had an affair over a decade ago. An aspect of this which has, surprisingly, just hit me now is this same phenomenon: I know they had sex in our bed and discussed our rather poor sex life.
It's the same vibe as friends ganging up on you, but worse: wife brings a horrible man into your marriage, and they form an alliance against you.
How strange, and how deeply unpleasant, that these thoughts have taken almost fifteen years to surface.