The question is a sad one. His kin were not perfect by any means, and most were difficult to convince down the Way of the Voice. Still, they were his kin. Alduin could not have been helped but the others..

"Niid. None who shared the skies with me are here, although perhaps the coming days will change that. I have much more distant kin, however. Ryu is not as I am, but he is dragon regardless."