If you are the parent or the device owner, there are exactly two official ways past a forgotten Screen Time passcode, and both live inside Apple's own tools. There is no third-party unlock that does it without either erasing the phone or already knowing the Apple Account.
Route 1 — reset it from the device itself (fastest). Settings > Screen Time > Change Screen Time Passcode > Forgot Passcode? On iOS 17 and later this asks for the Apple Account that set the passcode and lets you set a new one, keeping all existing limits and app data. On older iOS versions the same screen offers "Sign Out" after entering the Apple Account, which clears the passcode but also clears the Screen Time configuration.
Route 2 — the Family Sharing organizer. If the child's device is in your Family group and you are the organizer, the Screen Time passcode you forgot can be reset from your own device: Settings > Screen Time > [child's name] > Change Screen Time Passcode > Forgot Passcode, authenticated with your Apple Account. This is the cleanest path because nothing is erased and the child's device never needs to be touched.
Route 3 — erase and restore. If neither account is recoverable, the only remaining option is a restore, which erases the device. Apple Support will do it with proof of purchase; a Genius Bar appointment with the receipt is the reliable route.
Two things worth knowing before you try: Activation Lock survives an erase, so a "passcode bypass" service that promises otherwise is either using your credentials or replacing hardware. And if the passcode was set by the child on their own Apple Account, you may not be able to reset it at all — in that case, removing the device from the family group and re-enrolling it is the correct move.
For families running mixed devices, the practical setup is Screen Time on iPhones and a monitoring dashboard for the Android, Windows and Mac machines, which is what Ultimate Phone Spy covers (system requirements, plans). Keeping the iPhone side on Apple's own controls avoids exactly this kind of lockout.