The girl comes crawling to him once. The other firstborn Cynara mentioned. He knows from her scent, that metal and soil of dragon's blood; he knows this is another of his half siblings. One that shouldn't have lived, just like him.
The dragon lore says a dragon would bond once with its star, the source of its power. Their firstborn would mark the completion of the bond. The bond would remain active as long as the child lives. If the star dies, so would the dragon. If the dragon dies so would the star. It shall happen as long as the bond remains active.
