Sharing is caring, but there are limitations:
You can share new brushettes. Putting up a box for your household with a bunch of function is typically what is Brushette about.
You should NOT share used brushettes (that have been in your mouth), nor the neck adapter. Aside from general hygienic concerns, there’s also a risk of transmitting diseases that are generally transmittable by blood, like Hepatitis C.
You could share your electric toothbrush handle.