Oh, brother.
Bad sibling relationships can be exacerbated, if not downright created, from selfish parents who like to do things for show, rather than for caring directly about them.
God cares, of course. A lot of bad consequences can be reaped through sibling bickering. If siblings give each other the devil, then they get the devil from one another too. It’s inexorable. This isn’t letting a field be fallow, this is sowing it with poison.
Your post is one of best I have ever read on the subject. It is the absolute truth what you claim about bad sibling relationships. My siblings and I were always given the message that family was the enemy; just because my father wasn’t willing to live with the choice he made.