Despite being twins, Arcadio Segundo and Aureliano Segundo serve as foils to each other. As children, they were identical in both appearance and behavior, and other family members even speculate that the twins themselves have forgotten who was whom, as they frequently exchange identities. As adults, however, the two twins develop highly contrasting personalities. This contrast becomes apparent in the narrator’s description of Arcadio Segundo’s preoccupation with cock-fighting:
He soon displayed in the cockpit the wisdom that Father Antonio Isabel had given him, and he made enough money not only to enrich his brood but also to look for a man’s satisfactions. Úrsula compared him with his brother at that time and could not understand how the twins, who looked like the same person in childhood, had ended up so differently. Her perplexity did not last very long, for quite soon Aureliano Segundo began to show signs of laziness and dissipation. While he was shut up in Melquíades’ room he was drawn into himself, the way Colonel Aureliano Buendía had been in his youth.
Úrsula, their grandmother, reflects upon the profound differences between the two twin brothers. While Arcadio Segundo is interested in sports and competition, Aureliano Segundo remains “shut up in Melquíades’ room,” avoiding others, speaking to ghosts, and attempting to solve the mysteries of Melquíades’s occult notes. Ultimately, however, Úrsula finds that she is not surprised by this contrast, as both brothers reflect their namesakes in various ways at this early point in the novel. While the first Arcadio traveled the world as a sailor, engaging in illicit activities, Aureliano had been studious, spending long hours in his studio. Ultimately, however, the brothers diverge from their namesakes in pivotal ways, slightly undermining the relationship in the novel between names and destiny.
Fernanda del Carpio and Remedios the Beauty serve as foils to each other throughout the novel. Both are members of the fourth generation of the Buendía family, and both are exceedingly beautiful. Though the two women both serve as queens of the same festival before disaster strikes, their personalities are starkly contrasting. Some of these differences are underscored in a passage that describes Remedios the Beauty's response to the influx of American visitors to Macondo:
Remedios the Beauty was the only one who was immune to the banana plague. She was becalmed in a magnificent adolescence, more and more impenetrable to formality, more and more indifferent to malice and suspicion, happy in her own world of simple realities. She did not understand why women complicated their lives with corsets and petticoats, so she sewed herself a coarse cassock that she simply put over her and without further difficulties resolved the problem of dress, without taking away the feeling of being naked, which according to her lights was the only decent way to be when at home.
Fernanda del Carpio was raised in a highly traditional household, and as a result her manners are prim and proper. Despite the heat, she wears heavy and conservative clothing and treats her new family with rigid formality. In contrast, Remedios the Beauty is unaffected by social customs and pressures, acting in a highly natural manner and eschewing all "corsets and petticoats." These two beautiful but very different women are presented by the novel as foils to each other.