No, it is not necessary. Although the trip is taken as a group, each traveler must have their own individually approved ESTA visa. There is no difference between applying for the ESTA visa individually or as a group, except that in the latter case, all visas can be paid at once in a single payment.
Many users may be confused when submitting the application as a group as it is a bit more complex and requires the creation of a group contact person who is responsible for managing all applications. In these cases, we simply advise that the visas be submitted individually.
