each
When two things are right next to each other, like two people in a relationship who just can’t be friends. It’s called 'each' and it’s basically a side-by-side slap in the face.
My ex and I are 'each' because we can’t be friends and we hate each other.
Grace and Ricardo are 'each' because Grace says they aren’t just friends and Ricardo is annoyed.
My brother and his friend are 'each' because they’re best friends and also best enemies.