I think of Adam & Eve as being familially related, at least genetically so. Eve was created from the rib of Adam, right?
Perhaps this alludes to the admonishment against immediate gratification of sexual desire, forbidding incest, if you will. And perhaps extending that theory, a further lesson on controlling one's desires in all areas when acting in the moment may be wrong, while future results may be devastating.
Kinda like buying a home when your income is shaky & you get a loan for the full amount, including down payment, & know that the interest rate is flexible, & your spouse doesn't want to stay at their job, & your kids' college plans include private schools, & your credit cards are maxed out.....but STILL you have to, have to 'go for it'.....ah, the disasters, the dangers of immediate gratification when all along you KNEW better. Homelessness is the disaster you could have averted, if only...
Ah, but I digress....the forbidden fruit was, in my opinion, the lesson for Adam & Eve that one must put aside immediate gratification for the wiser vision of how one's actions of the moment may create a future that is not healthy, wealthy, or wise.