My sister abused me mentally growing up. She said she’d wish I’d never been born when I was. She called me names and asserted her power on me. She thought she was better than me because she was older.
If I was born first and my parents told me “You’re going to have a little sibling” I would have said “oh”. I wouldn’t make a very influential older sibling. I would still lack an “identity” of an “older sibling”. It would be different. I can’t imagine it. But it would be different. But I’d still be SZ. That’s not the reason why I was SZ.