Gotcha - center brake light comes on with the headlights.
Now - I'm not certain how the headlights on a Reno are wired - I believe that's a Daewoo built vehicle not a true Suzuki - so the wiring may differ from Suzuki's norm which is negative switched.
Anyway - if you have positive switched headlights and a defective lighting system grounds - it is theoretically possible to have current flowing through the headlight filament, and instead of going to ground, going through various park light & tail filaments into the brake light circuit - if this is the case you should see other strange combinations of light brightness as lights or switched on and off.
What I would do is take a look at the wiring in the vicinity of the headlights and tail lights - look for wires going to bolts on the frame - remove the bolt, clean up the terminal that's underneath it and reconnect. Also remove and check the actual headlight & tail light connectors for corrosion and clean and/or replace as required.