If you often change up your look or have your spouse use your iPhone, you should definitely set up a second Face ID. Under the Face ID settings, Apple has long offered an Alternate Appearance feature that lets you set up two Face ID profiles on your iPhone. To use it, go to Settings -> Face ID & Passcode -> Set Up an Alternate Appearance. Now, follow the on-screen instructions and move your face around to add a second Face ID.
If the Face ID on your iPhone is malfunctioning or isn't working at all, you can start by cleaning the camera and sensors, then restart your iPhone.Check for iOS update and reset Face ID in the settings, or try resetting and reconfiguring Face ID settings. If the issue persists, consider contacting Apple support or visiting an Apple store for further assistance, as there might be a hardware issue.