From FCC: https://www.fcc.gov/general/general-mobile-radio-service-gmrs

Go to the FCC site and read the whole page.

:An FCC license is required to operate GMRS system. Licenses are issued for a five-year term and can be renewed between 90 days prior to the expiration date and up to the actual expiration date of the license. After a license expires, an individual must request a new GMRS license.

A GMRS system licensed to a non-individual prior to July 31, 1987 is also eligible for renewal, but the licensee may not make any major modification to the system.

You may apply for a GMRS license if you are 18 years or older and not a representative of a foreign government. If you receive a license, any family member, regardless of age, can operate GMRS stations and units within the licensed system.

The FCC service rules for the GMRS are located in 47 C.F.R. Part 95 Subpart A. You can find information about GMRS licensing in the rules."