Dragon Prince Series by Melanie Rawn

Melanie Rawn's best-selling debut is a novel of love and war, magic and madness, and deadly dangerous dragons that hold the secret to unimaginable wealth that could prove key to mutual peace-or a bloody tyrant's reign. And among it all, an idealistic young ruler struggles to civilize a culture that understands the strength of the sword-but has yet to discover the true power of knowledge.

As High Prince and Princess, Rohan and Sioned must keep both the peace and the secret of the dragons. But the legacy of their evil predecessor remains-and as their son Pol grows up, the kingdom splits in what may become a bloody battle for the crown. To make things worse, a long-vanquished foe vows to destroy the Prince. The only hope of defeating their dark sorcery lies in reclaiming the knowledge so carefully concealed in the long-lost Star Scroll.

Andry, the new Sunrunner Lord of Goddess Keep, must master potentially deadly magical knowledge before he can confront the ancietn foe who nearly destroyed the Sunrunners ages ago.  But the enemy is mobilizing to strike again, drawing on forbidden lore to play an ever-shifting game of treachery and betrayal.