I have a bathroom that was re-wired to add a bathroom fan some years ago. I am wondering if it was wired correctly. Originally, I believe the overhead light was wired in a switch loop to a single wall switch. When the fan was added, two new switches (for the fan, and the fan's light) were added on the wall.
To make this work, the electrician pulled a new wire pair from the switch to the overhead light. The old wire pair is now in parallel with the single circuit from the breaker panel, it provides power to the three wall switches. All of the neutral wires at the light are tied together, and all of the neutral wires in the wall are tied together. Because there are now two wire pairs between the overhead light gang box and the wall switch gang box, this creates a circular neutral path.
In the image, the neutrals are tied together at A and B, and the circle / parallel path for neutral is created by cables 1 and 2. Grounding wires are not shown.