Almost all timeshare contracts include a perpetuity clause that obligates the grown children of timeshare owners to accept their parents' timeshare upon their parents' passing. However, this problem is easily solved by any probate attorney for a nominal fee. So if this is the only reason you want out of your timeshare, it's probably best just to keep it, rather than pay a cancellation company thousands of dollars to cancel it.
When you die, it's cancelled!