I think that only a part of Kirkbride's stuff makes sence.
From this I see only that Wulfhart seemingly knew how to shout and passed his knowledge to Hjalti. That doesn't make him a Dragonborn. The Greybeards can teach you shouts, and from how they do that, I totally can see Wulfhart doing the same with Hjalti, and none of the Greybeards is a Dragonborn.
I'm not sure whether the title of Ysmir means a Dragonborn, I have a feeling that although those two things coinside in several cases, they are not actually the same.
I think that only a part of Kirkbride's stuff makes sence.
From this I see only that Wulfhart seemingly knew how to shout and passed his knowledge to Hjalti. That doesn't make him a Dragonborn. The Greybeards can teach you shouts, and from how they do that, I totally can see Wulfhart doing the same with Hjalti, and none of the Greybeards is a Dragonborn.
I'm not sure whether the title of Ysmir means a Dragonborn, I have a feeling that although those two things coinside in several cases, they are not actually the same.