Board Thread:Naruto Discussions/@comment-4700229-20141027210331/@comment-28861328-20141105220115

NeedleJizo wrote: Well Obito's relationship to Madara was never explicitly stated, he simply called him "my precious forefather". It leaves a lot open, like the relationship between Shisui and Kagami.

I'm guessing that wasn't clarified in the databook, either.

No, it was clarified in the chapter. Tau, at the time, pointed out that the word used directly refers to a blood-related ancestor. Japanese words, unlike some in English, can be very specific as to their meaning.