Skip to Content

Why can my brother open my Face ID?

There are a few potential reasons why your brother may be able to open your iPhone using Face ID even though it is set up for your face only:

You two look very similar

If you and your brother have similar facial features and structure, there is a chance that your iPhone’s Face ID system may mistake him for you. Face ID uses advanced neural networks to map and recognize faces, but it is not 100% foolproof. Siblings often share a lot of genetic similarities which can confuse Face ID.

You may have set it up incorrectly

When you first set up Face ID, did you accidentally register your brother’s face too? If you went through the initial setup process together and both looked at the phone, it’s possible his biometrics were added as well. Check your Face ID settings to see if “Set Up an Alternate Appearance” is enabled for multiple faces.

He has access to your passcode

Even with Face ID enabled, your iPhone will prompt for the passcode under certain conditions – like after a restart, if it hasn’t been unlocked for 48 hours, or after 5 failed Face ID attempts. If your brother knows or has access to this passcode, he can bypass Face ID and unlock your phone that way.

How Face ID Works

To better understand why your brother may be able to get into your iPhone, let’s take a quick look at how Face ID functions:

Face map

When you set up Face ID, your iPhone takes an infrared scan of your face and uses this to generate a mathematical model or map of your facial structure. Key data points like the distance between your eyes, shape of your cheekbones, position of your nose and lips, etc. are all recorded.

Neural networks

Your face map is then used to train advanced neural networks on your iPhone’s processor chip. These neural networks contain millions of connections and patterns that allow Face ID to recognize your face amongst a wide variety of conditions.

Matching attempts

Whenever you attempt to unlock your iPhone using Face ID, a new infrared scan is taken. This capture is converted into another mathematical model and fed into the neural networks. If there’s a match, your iPhone unlocks. If not, Face ID blocks access.

Why Siblings Can Fool Face ID

Now that we understand Face ID basics, let’s look at some specific reasons a sibling like your brother may be able to bypass this security:


Siblings typically share around 50% of their DNA. You directly inherit half your genome from each parent, while your brother inherits a different random mix of 50% from the same parents. This means siblings can often look very physically similar. If your face structures match closely enough, Face ID can mistake your brother for you.

Similar facial features

In addition to genetics, siblings also usually share common facial features like eye color, hair color, nose shape, lip fullness, etc. These similar physical traits increase the chance that your brother could fool Face ID. Even small amounts of facial resemblance could confuse the neural networks.

Training bias

Face ID’s neural networks are trained on millions of facial images. However, most of that training data likely comes from unrelated people. There may be insufficient data on sibling faces for Face ID to learn how to distinguish between them accurately.


For identical twins, fooling Face ID becomes even easier. Identical twins share 100% of the same DNA rather than just 50%. Their facial features are even more alike. Apple concedes that Face ID cannot tell apart identical twins.

How to Improve Face ID Security

If you want to prevent your brother or other siblings from accessing your iPhone via Face ID, here are some tips:

Use a passcode

Set a strong alphanumeric passcode on your iPhone (at least 6 digits). This provides backup protection if Face ID fails or is bypassed. Don’t share this passcode with siblings or anyone else.

Disable alternate appearance

Go into Face ID settings and turn off the “Set Up an Alternate Appearance” option. Only your primary appearance will be registered. Re-enroll your face map without your brother present.

Add more angles

Train Face ID by registering your face from multiple angles during setup – straight on, sides, up, down. Capturing your face map at various orientations can improve recognition.

Use attention detection

Enable “Require Attention for Face ID” in settings. This makes Face ID confirm your eyes are looking at the iPhone before unlocking. Your brother can’t just show your phone his face while you’re not paying attention.

Turn on Face ID verification

Go to Apple ID settings > Password & Security > Use Face ID For and enable verification for iTunes & App Store purchases. This adds an extra Face ID check before spending money.

Troubleshooting Face ID Issues

If you take the steps above but find your brother or siblings can still get into your iPhone with Face ID, try these troubleshooting suggestions:

Delete face data

Go to Settings > Face ID & Passcode and completely reset Face ID by tapping Reset Face ID. Then set it up again from scratch ensuring no one else is looking at the phone.

Check for issues

Inspect your phone closely for any damage or issues with the infrared camera and dot projector used for Face ID on the front. Cracks, scratches or other physical problems can affect facial scans.

Disable then re-enable Face ID

Toggle Face ID off completely under Face ID & Passcode settings, and require your passcode to unlock the phone. After a day or two, turn Face ID back on and rescan your face from multiple angles.

Contact Apple Support

If the problem persists after trying the above, reach out to Apple Support. They can run diagnostics, check logs for any Face ID errors, and ensure nothing is configured incorrectly on your iPhone.

Frequently Asked Questions

Here are answers to some common questions about siblings and Face ID:

Can identical twins fool Face ID?

Yes, Face ID cannot reliably tell apart identical twins, triplets, etc. Their DNA and facial features are too similar. You should not rely on Face ID to secure data from an identical twin.

Does Face ID work with siblings who look alike?

It depends on the similarity level. Siblings with only vaguely similar appearances likely won’t fool Face ID. But those who look very alike may be able to unlock each other’s iPhones in some cases.

Can I make Face ID more secure against siblings?

Yes, you can improve security by turning off alternate appearance, adding more face angles during setup, using attention detection, and enabling Face ID verification for purchases.

Why can my fraternal twin sibling open my Face ID?

Fraternal twins have the same amount of genetic overlap as regular siblings (around 50%). If your fraternal twin has a very similar face structure, the neural networks can get confused and match their face to yours.

How can I tell if someone else’s face is registered?

Go into Settings > Face ID & Passcode. Scroll down and check if “Set Up an Alternate Appearance” is enabled or disabled. If it’s enabled, another face is registered.


In summary, siblings can sometimes fool Face ID and gain access to each other’s iPhones due to genetic similarities in their facial features. This is most likely with identical twins but can also happen with regular brothers and sisters depending on how much they look alike. Improving security is possible by taking measures like using a passcode, restricting alternate appearances, adding more face angles, and enabling Face ID verification. With proper precautions, you can help keep your iPhone locked down against siblings and enjoy solid protection from Face ID’s advanced facial recognition capabilities.