as suspected, Kaito is the son of Okitsugu and half brother to Mio, Mio new it when she met Kaito, Okitsugu didn't want anything to do with Kaito because of what Kaito's mother tried, Mio met Kaito and saw the type of person he was and how he had been living, she was proud of her nii-chan and wanted to protect him, Okitsugu found out about Kaito, at first he was upset that his daughter was around Kaito, with a little push from his daughter and Seiji, it looks like wants to make amends for abbanding Kaito until now, Mio really wants a relationship as a family with Kaito and the rest of her family, Kaito appears to have accepted what happened,it could take time but it looks like he will accept things to a certain extent, like Nagi, Kaito would like a relationship with his father and sister
thanks and keep up the good work