for simplicity lets call the characters clones. Sometimes a clone might not be allowed to see another clone in order to prevent a time paradox (although that could just be the characters simply being careful).
In Dexter's Laboratory
dexter and his 3 clones (who are different ages) team up to beat mandark, who also
has 3 clones.
I have also seen this trope in Redvs Blue
blood gulch cronicles church had quite a few clones, one of them had a different color for some reason.