You can use up to five different fingerprints with the Touch ID sensor that comes with certain iPhone and iPad models, so one of those fingers could be from a spouse. Apple’s support site does warn, “Each new print might make fingerprint recognition take slightly longer,” and keep in mind that certain circumstances require the numeric passcode instead of Touch ID to unlock the device.
Opening the Touch ID & Passcode controls in the iOS Settings is one of those situations where you do need to enter the four- or six-digit numeric passcode for the device.
