If I were your "keeper" (or your "care-taker" or "legal guardian" [because you had, e.g., been declared by a Court of Law to be mentally incompetent]), wouldn't I have a right - nay, an obligation - to see to it that you got enough bed rest, didn't eat too much, didn't indulge in any excessive drinking, etc. - sort of like how I treat my 9-year-old son?
Wouldn't I, as your "keeper," be entitled to curtail your seeing your friends, if I thought they were a bad influence upon you? Etc.
And how could we all be each other's keeper - i.e., how could it possibly be a reciprocal relationship?
It is a logical impossibility.
Even substituting the word "help-mate" in place of "keeper" is problematic - God ordained only that "man and wife" would (have to) be that to each other.
Regards,
So when God asked Cain “Where is Abel your brother?” His question was inappropriate or wrong because Cain is NOT his brother’s keeper and shouldn’t know at any given time where he is?
Were God to ask me where my brother is, I’d answer I suppose, “Lord, I believe he is up in (city, state), working on his house.”
Not, essentially, “How should I know? What do you mean by asking me that?” and correcting God’s question to me, as it were.