Why do my rear running/turn signal lights come on when I apply the brakes!!?

Yes... When i hit the brakes the two back lights that come on are the two same that come on as run lights and blinkers. Possibly someone crossed some wires...Idk

The brake light and the turn signal light uses the same bulb and same circuit (bulb element) which is just a 'brighter bulb element' than the running light bulb element is .. IF wired for trailer towing, that'd be a good place to start looking .. May need some 'hands-on' help with this as troubleshooting can get a bit tricky at times, even for a seasoned mechanic... Good luck with it!