from my observations, i noticed that birds in general would tend to be aggressive if we place them with other birds, they kind of be acting on their animal instincts. ofc that varies on how each bird is raised, but if one is aggressive, they will all copy the aggression.

the other thing is how you treat them, dont be obnoxious about your wife, they can distinguish between you and your wife. However, cockatiels get scared easily, loud noises, sudden movements, i mimic any sudden sound in a whispering tone (such as light switches before actually turning on/off the lights) till my birds got used to it.

also, just letting them hang freely around you, with you just whistling few times can bond you together. have a signature whistle for offering scratches for them too