Responses
Shizu is a confirmed alpha (vol 4) but I agree with you about the younger boys. But I thought Minato might also be an alpha who is similar to the sensei in the spinoff (aka not as possessive and aggressive).
Aoi is without a doubt an alpha - like Haa-kun's mini-me
My guess is the eldest daughter is an alpha, eldest son is an omega and the youngest is an alpha