If you don't mind me asking, is it confirmed that the first brood all had the same body-type?

Considering Middy has shown himself in 3 forms ranging in size and wildly different shapes (dragon pup form verses miles long serpent) and the different dragon sizes and shapes from the individual broods, I wonder if Bahamut was just genetically predisposed to have different appearance, or if a dragon's appearance directly correlates to their current level of aether/power.