Fantasy series read in the early 2000's where the main character is possessed by a dragon demon and can transform into a humanoid dragon

Question

The main character becomes possessed with a dragon demon spirit and is able to transform into a blue/red humanoid dragon shape if he allows the spirit to take over. The over all antagonist, I believe, is a jealous family member who ends up bonding with a green/yellow dragon demon spirit that tries to unleash the others of its kind. The love interest is a young lady that ends up being a part of a family who have owl familiars/ spirits and are the sworn enemies of the dragon spirits and those who wield them and are responsible for the dragon spirits being locked away at the beginning of the series.