how to see other phone screen on my phone?

Short answer: you cannot view another phone's live screen from your own unless the person holding it actively shares it. Android's capture API demands an on-screen consent prompt every session and iOS has no remote-capture API at all, so every product claiming silent screen viewing is stalkerware.

The consent-based options, cheapest first.

• Google Meet (meet.google.com) — the owner taps Share screen, you watch from any browser. Free, works on Android and iPhone.
• FaceTime screen sharing on iOS 15+ — start a call, tap Share My Screen. Built in, free, and it is the simplest way to walk a parent through a settings problem.
• Microsoft Phone Link on Windows mirrors a linked Android handset's screen and notifications, but pairing needs the phone in hand and a confirmation tap on the device.
• scrcpy over USB, with developer options enabled by the owner, gives the lowest-latency mirror and stays entirely local.
• TeamViewer QuickSupport or AnyDesk for remote support of a relative's phone — an on-device code is required, which is exactly the control you want.

Why there is no covert version. Live screen capture is the most invasive permission a phone exposes, so both platforms gate it behind a visible dialog. Tools that appear to skip it abuse accessibility services; Play Protect flags them, the phone's security posture degrades, and using one against an adult is unlawful interception under 18 U.S.C. 2511 and the Computer Misuse Act, with stalking statutes on top in most US states.

Where ours fits. Ultimate Phone Spy is a history dashboard, not a mirror: on Android 4.0+, Windows and Mac it shows what happened on a device you administer — SMS threads, calls, location, web history, installed apps — at https://ultimatephonespy.com/parental-control-features. It has to be installed on the device with the user's knowledge, it cannot be pushed remotely, and it does not cover iPhone.

For a child, the free answer covers most of the need: Screen Time on iOS or Family Link on Android for app limits, location and who they can contact — plus asking them to share their screen when something feels wrong. That conversation usually reveals more than a mirror ever will.