I tried to find something in the mint family that had compound leaves with the typical square stem yesterday and didn't find anything. I know there are a few other plants with square stems so tried to find some - according to this U of Wisconsin botany page, the combo of square stem and opposite leaves is almost unique to mints, but Verbenaceae and some Urtica also do. I haven't looked for compound leaves in those yet:
http://www.botany.wisc.edu/cou...
Edit: According to eFloras in Flora of China some Verbenaceae do have compound leaves.