Board Thread:Boruto Discussions/@comment-33066801-20170910125949/@comment-30323490-20171007115627

A Hamura descendant requires a byakugan from a Hyuga member to awaken the Tenseigan. In other words, the combination of their chakra.

In Boruto's case, maybe the Jougan requires the chakra from a Hagormo descendant (Naruto, who's six paths chakra probably resembles Hagormo's and is the reincarnation of his son) and the chakra (byakugan) from a Hyuga member (Hinata).

So, in my opinion, the Jougan is somewhat of a twin brother of the Tenseigan. The Tenseigan requires the mix of Hamura's part and the Hyuga part, and the Jougan requires the mix of Hagormo's part and a Hyuga part.

And this would kind of explain why Toneri knew about the Jougan and it's prophecy. Since he is a Hamura descendant, he would've been unable to awaken the Jougan, so he went for the next big thing (or the equivalent thing) and begun his hunt of the tenseigan.