Dragon Disciple's get Form of the Dragon I/II and "must assume the form of a dragon of the same type as his bloodline"
With some of the new Bloodlines in Legacy of Dragons you cannot change into the correct form with Form of the Dragon I/II and instead would need the new variations on that spell instead.
e.g. One of the esoteric bloodlines needs Form of the Alien Dragon.
As I read it, RAI a DD with those bloodlines would gain the correct Form of the Dragon for their bloodline instead of the default one, correct?
Otherwise, what Dragon would they turn into?