Full Idea
A may be a counterpart of B according to one counterpart relation (similarity of origin, say), but not according to another (similarity of later history).
Gist of Idea
Things may only be counterparts under some particular relation
Source
Penelope Mackie (How Things Might Have Been [2006], 5.3)
Book Reference
Mackie,Penelope: 'How Things Might Have Been' [OUP 2006], p.86
A Reaction
Hm. Would two very diverse things have to be counterparts because they were kept in the same cupboard in different worlds? Can the counterpart relationship diverge or converge over time? Yes, I presume.