itd make more sense for tsubame to be kum and hachis son because he cries a lot like kuma and is not good at studying like both of his parents. mitsu and suzu are both intelligent/good at studying which miyama is, so itd make sense for him to be their son. but its still cute that they differ a bit from their parents while looking similar
Miyama has an older sister though (Yoruba, I think) so she may be more like their parents. Enough so he felt he needed to take matters into his own hands. I find Tsubame rather refreshing though.
itd make more sense for tsubame to be kum and hachis son because he cries a lot like kuma and is not good at studying like both of his parents. mitsu and suzu are both intelligent/good at studying which miyama is, so itd make sense for him to be their son. but its still cute that they differ a bit from their parents while looking similar