Actually my step sister's step daughter's I knew were sick and I got asthma from them when they had my and my family over.
Me
I have asthma and so does my dad. I think my daughter might too. It can be hereditary, but I was informed by my allergist mine is a form of my allergies. I believe it can be environmental, but there are probably other forms and other ways to get it. Also like someone said before anything can happen in the manga lol
Im thinking what if the older brother is good at communication but the little one is smarter so when it come to their business the little one would be suit the most but the older now this and jealous for it and i think he done something to the little brother to make him sick i mean he started sick when he turned 5 and i think rather than the older brother people seems to remember the little one more like the case which in circus the memories show that old man the shy one and that is the little one
btw comment your thought below