https://support.apple.com/en-gb/HT208108
> The statistical probability is different for twins and siblings that look like you [...] If you're concerned about this, we recommend using a passcode to authenticate.
They know, they mention it, they suggest a passcode.
Note that identical twins do not have matching fingerprints.
https://support.apple.com/en-gb/HT208108
> The statistical probability is different for twins and siblings that look like you [...] If you're concerned about this, we recommend using a passcode to authenticate.
They know, they mention it, they suggest a passcode.