The Blue Dragon Dragonborn clearly knew this as well, holding his head high as he said as a matter of course, "If I win, let me leave; if I lose, I will swear loyalty to you."
"Good," Gaven agreed without hesitation, nodding his head.
Upon first sight of the other, Gaven had already recognized that this was not just any ordinary Dragonborn but rather a Half-Dragon; one could only claim the title of Half-Dragon if one of their parents was a True Dragon. Otherwise, they could only be collectively referred to as Dragonborn or, in other words, creatures of Dragon Blood.
Half-Dragons are classified as part of the Dragonkin, not humanoid beings.