The grandma and the brothers are not related however the brothers remind her of the times with her son. BTW the grandmas son died
Basically Granny lost her son and his wife on the same flight that Ryuu and Kotaro lost their parents. So she adopted the two of them and one of Ryuu's requirements to be with granny and going to school and all was to be the day care helper cause no students ever sign up. In some moments Granny reminisces about her son and daughter in law vicariously through what Ryuu and Kotaro are doing
oooohhhh thaaaanks that makes so much more sense than what I was thinking.
thanks for clearing it up :)
I'm a little confused (I haven't finished the whole thing btw) but what exactly is the relationship between the brothers and the grandma? They're not her biological grandchildren right? She states that many times and her son looks nothing like their father so what's happening?