Board Thread:Lore Discussion/@comment-11923066-20130126013641/@comment-231553-20130317080033

it seems that dragons in general have very randomized forms in Dark Souls, at least the descendants of the verlasting dragons. The gaping dragon, the cyclopian black dragon, the stoen dragon, and so on, the stone dragon being the most closely related of the everlasting dragons.

The Hellkite is in fact a Drake, which is a lesser but power relative of a dragon.