
Wait that means that Yuri is Rio's close cousin?! And if they had a son he would his cousin too........

As far as I know Marriage between cousins isn't that common anymore xD children born from incest do have a lot more chances of having certain disabilities and such.
Aside from that marriage between relatives was a thing some time ago to "preserve" the lineage or something xD
He explained at the start that their families would marry each other for centuries to preserve their powers so I guess that they could even be first cousins but it's not like they'd give a sh!t or two about it
It's amazing how a birthday episode has updated on my birthday (≧∀≦)