Currently it is US Policy to retain the fingerprints of minors collected as part of the Trusted Traveler (GOES, PreCheck) programs indefinitely
These fingerprints are collected as part of the enrollment process to these Border and Airline Security programs. Parental consent must be given to collect the fingerprints, however the minor is currently unable to request that the fingerprint file be deleted once they turn 18. A election made by the parent when the person was a minor should be confirmed by the child once they turn 18. There is no opt out currently
Minor children's biometric data should be automatically removed at the end of enrollment with the Trusted Travel program or they should be given the opportunity to request that their fingerprints be deleted once they reach majority age