"Thou dost me injustice," said the Templar; "by earth, sea, and sky, thou dost me injustice! I am not naturally that which you have seen me, hard, selfish, and relentless. It was woman that taught me cruelty, and on woman therefore I have exercised it; but not upon such as thou. Hear
me, Rebecca – Never did knight take lance in his hand with a heart more devoted to the lady of his love than Brian de Bois-Guilbert. [...] Yes, my deeds, my danger, my blood, made the name of Adelaide de Montemare known from the court of Castile to that of Byzantium. And how was I requited? – When I returned with my dear-bought honours, purchased by toil and blood, I found her wedded to a Gascon squire, whose name was never heard beyond the limits of his own paltry domain! Truly did I love her, and bitterly did I revenge me of her broken faith! But my vengeance has recoiled on myself. Since that day I have separated myself from life and its ties – My manhood must know no domestic home – must be soothed by no affectionate wife – My age must know no kindly hearth – My grave must be solitary, and no offspring must outlive me, to bear the ancient name of Bois-Guilbert. At the feet of my Superior I have laid down the right of self-action – the privilege of independence. The Templar, a serf in all but the name, can possess neither lands nor goods, and lives, moves, and breathes, but at the will and pleasure of another." (24.52)
Now we know the secret of Bois-Guilbert's broken heart. He loved a woman once, but while he was off fighting in the Crusades and winning glory in her name, she married some small-fry squire. Heartbroken and enraged, Bois-Guilbert swore off women entirely; as a Knight Templar, he cannot marry, have children, or even own his own home. As Rebecca points out, this is a rather self-punishing form of revenge: we can't see how it's going to help him get even with the woman who broke his heart. However, it does give us an indication of how proud Bois-Guilbert is, how serious he is about his honor, and how much he must honestly love Rebecca to be willing to break his oaths and compromise his pride on her behalf. Bois-Guilbert's genuine love for Rebecca saves him from being an almost cartoonish villain. Like De Bracy, he is more complex than he originally appears.