After Candide had proven himself worthy, why didn't Cunegonde's brother still not want them to get married?
When the commandant says he can talk with Candide because they are both German in Chapter XIV, the two rejoice to see each other. However, in Chapter XV, the baron, who has called Candide his brother and savior, learns that Candide intends to marry Cunegonde and says angrily,
You insolent wretch!.... How impudent of you even to think of marrying my sister who has seventy-two generations of nobility behind her! You ought to be ashamed of yourself for daring to mention such an audacious scheme to me!
When Candide retorts that rank should make no difference since he has rescued Cunegonde from the arms of a Jew and from the Inquisitor and, so, she is under great obligation to him. Candide adds,
Dr. Pangloss always told me that all men are equal, and I will certainly marry her.
Striking Candide across the face, the "Jesuit Baron Thunder-ten-tronckh" shouts, "We'll see about that!" Instantly, Candide draws his sword, killing Cunegonde's brother, but when he withdraws his sword, he cries.
Dear God!....I've killed my former master, my friend, my brother-in-law! I'm the kindest man in the world, yet I've already killed three men, and two of them were priests.
In this scene, Voltaire satirizes the Jesuits who, as priests, take a vow of humility. But, the brother of Cunegonde makes Candide wait for him and is so haughty that he thinks Candide unworthy of marrying his sister. And, although Candide murders with alacrity, he believes himself "the kindest man in the world."