User blog comment:Jopjopjop/Volume 20 Spoilers/@comment-26865730-20150810190451

We are not told who the shrine Issei's father prayed to for a safe birth? In DxD-verse praying has an effect. Almost gotta wonder if Tiamat (she is a god in mythology) might have answered that prayer by giving Issei dragon power to survive till birth. That would complete his connection with all of the Dragon Kings and it would also be what attracted Draig. Much like the way Balor's conciousness summoned by Valerie attracted Gasper's Forbidden Balor View.

Even though it is not stated, I think there is an implied parallel to the evolution of Saji's SG after being exposed to Issei's blood and the evololution of Gasper's SG since he has been given the blood on several occasions. So I was just wondering if there might be a parallel in how a god level being might have caused the attraction of the original SG in both Gasper and Issei?