Does an owner record need to have a CKReference field or just the owned record?

I'm posting this in this forum because it will get more attention here. If I have two record types with a one-to-many relationship does the owner (one) record have to have a CKReference field or just the owned (many) record? If the owner record has a CKReference field, what is that field set to in the owner record?

Does an owner record need to have a CKReference field or just the owned record?
 
 
Q