Circuit troubleshooting. Need input on discovery
The first two, hot to ground and hot to neutral are normal and what you'd expect.

Voltage showing on from the hot to hot leg may not be a sign of any problem -- Voltmeters have a very high impedance, so any load at all on the other circuit can provide a path to neutral that will appear as 120V to the meter. This could be a lamp, a "smart switch" or outlet, a small night light, a cell phone charger, pretty much any load at all.