May contain plot details
In the Prologue of The Cruel Prince, it was said that Jude and Taryn looked just like their dad, Justin Duarte.
He was an interesting person, according to Madoc.
He loved swords since he was young. Instead of going to college after he came of age, he had an apprenticeship with a master swordsmith. Later, his skills became honed enough that he was eventually allowed into the Faerie Realms.
In the Faerie Realm he sort out Grimsen, who he forged a knife for and wanted to know what he thought of it. Grimsen told him that if he practiced for fifty years he might make the greatest blade ever made by a mortal man. He then told him that if he practiced for a hundred years, he might craft one of the finest blades made by anyone. None of it satisfied Justin. Grimsen then offered him a bargain that he would give him one of his secrets, so Justin could learn the practice of a hundred years in a single day. But only if he would part with something he didn’t want to lose. It is unclear if Justin took the bargain or not.
9 years later, Madoc got news of Justin's bragging that he could "forge faerie blades" and came to their doorstep. Madoc killed him with a sword to the heart.
He forged the sword Nightfell, which was gifted to Jude by Madoc in The Cruel Prince.