A careful examination of the story conclusively reveals that Armand was definitely not aware of his mother's ancestry. Note the way that when Desiree becomes aware of the dark skin of her baby, she goes to her husband, horrified and shocked, asking what the meaning of this is. The answer that Armand gives her clearly displays Armand's belief in his own pure bloodline and condemns her and his child for their racial impurity:
"It means," he answered lightly, "that the child is not white; it means that you are not white."
This harsh and cruel response clearly places the blame of their child's questionable race on Desiree, as Armand does not believe that he could ever be descended from any former slaves, as, we are told, he belongs to "one of the oldest and proudest" families of Louisiana. The way in which he treats his wife and child, after having been depicted as being so in love with them, clearly displays his ignorance of his own ancestry, which of course makes the ending of this excellent story bitterly ironic, as Armand realises that he blamed the wrong person.