I suppose what I was referring to, was you saying this sort of thing:
“the millions of posts, articles, news stories and pages, both paper and web pages dedicated to [siblings despising each other].”
You are aware of all of these millions of things which I have no particular reason to seek out. I see that human beings are complicated and any relationship can be fraught, even so, very few people choose to live in isolation.
There’s no evidence that sibling relationships are more fraught than parents and children, couples, grandparents, in laws, colleagues or friends. I really do not see a skewing towards sibling relationships as being tougher to navigate than the rest.
To me, it strikes me as a confirmation bias, that you seek out evidence to suggest that having siblings is a bad thing because you already believe it.
I’m not invested in proving that having siblings is amazing, but I did give thought to my family, how many children I have and the ages between them, with a view to giving them the best chance of getting along and supporting each other in the future based on what I know. Of course I don’t have a crystal ball, all I can do is give it my best shot. I don’t expect other parents to think it through, that may not be their style, but the fact the OP seems to be similar to me, wanting to give it thought, I am sharing that I believe it is better in the long run, throughout the generations, to have an extended family.