Any ideas how/why their connected?

Check for burned out tail,brake or turn signal bulbs. Your cruise is connected through the brake light circuit.

All lights work, but I did find that when I turn on the headlights the brake lights activate w/o pressing on the pedal. That explains why the cruise is shutting off.

Now I need to figure out why the brake lights are coming on w/o an input. Any ideas?

Sure seems like you have continuity between the two circuits, will your headlights illuminate when you hit the brake? A bad ground can also cause some strange things.

sounds like the brake sensor in your pedal is failing or some circuitry in there is shorted out causing the car to think that your brake pedal is depressed; hence your brake lights turn on. surprised it doesn't do it even during the day. check the brake sensor on your pedal.