“I live in Texas, the property that I bought had an unrecorded easement. I would like to know if it is possible for the people using this easement to legally have the width of it extended from about 12ft. to 20ft.? I know that if we end up going to court over this matter that they probably will be granted a prescriptive easement based on the amount of time that it has been used. But are they allowed to place another burden upon my property by extending the width to encompass more of the property?”
The answer depends on the history of your particular situation. In the same way that someone can obtain a prescriptive easement, an existing easement (regardless of how it was created) can be expanded in scope via prescription.
So, to use your example, if someone has a 12-foot-wide easement, but uses a 20-foot-wide portion of the property, they could get the right to the additional 8 feet via prescription. Similarly, if someone had an easement only for use as a driveway, but also used the same area of land for their sewer line, they could get that additional use (sewer line) via prescription.
As with any prescriptive easement situation, the specific facts will be critical. The exact requirements vary somewhat from state to state, but generally the use must be open, continuous, and without permission for the statutory period of time.