I don't have any siblings, but I notice that people close to me-- like my spouse-- develop more social anxiety over time.
I don't know if that's a product of living with someone who can't help but make you see how cruel the world can be, or if it stems from being close to someone who committs errors that render one ashamed of them, ashamed for them, and ashamed to be associated with them.
I'd like to believe the former. I suspect the latter.
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"Alas, our dried voices when we whisper together are quiet and meaningless, as wind in dry grass, or rats' feet over broken glass in our dry cellar." --TS Eliot, "The Hollow Men"