Best theory is that the Mist Nin's killed off Kimi's family because they were scared of their bloodline limit (similiar to the killing of people with Haku's bloodline limit)

Kimi is orphaned and some how Oro picks him up....

Would be interesting for a Zabusa vs Oro battle yes? It would have to end with Haku / Kimi calling it off and people taking their seperate ways.... This is just a thoery of course but Oro has to get involved at some point to take Kimi in.