What is each character's attitude toward Uncle Marcos?
Overall the family regards Uncle Marcos with a great deal of affection, though there is one exception. Most of what we learn about the family's opinion of Uncle Marcos can be found in the first chapter.
Nivea, Marcos' sister, has a great fondness for her eccentric brother. In the first chapter we see her throw herself onto his coffin shouting words of mourning when his body is returned ravaged with an African plague. She also overlooks many of his odd habits, such as donning a loin cloth when relaxing in the yard on a hammock. When Uncle Marcos disappears after taking a flight in a large balloon, she cries inconsolably. This being noted, Nivea is not totally blind to the stress that her brother's presence in her home can cause, as she does share her husband's relief when he takes off on new travels in the middle of the night.
Severo does not share this affection for Uncle Marcos with his wife. We see that he is annoyed by Marcos' odd habits, and believes that his brother-in-law has "the manners of a cannibal." These feelings are clearly not as strong as his care for his wife, as, in spite of his annoyance, he allows Marcos to stay for long periods of time in the family home.
Clara is perhaps the closest of all of the family members with her Uncle. Although her uncle is away for long periods of time, she is able to recall his exact look due to her fondness and is always excited when he comes home to stay.Not only does she participate in a divining scheme with him, she is the only child with enough patience and interest to sit with him and hear his many stories about his bizarre travels. The evening that he disappears on his travels, she becomes so distraught that she begins to sleep walk and suck her thumb.
Chapter one also notes that all of the del Valle children enjoy having him in the house when he comes to stay, but there are no specific examples of their interactions with him, the way we see with Clara.
Finally, although Uncle Marcos leaves us in the first chapter, his memory is such that a love for his spirit is seen in at least two more generations. In chapter four, Uncle Marcos' "magic books" are special enough that Blanca brings them to Tres Marias to share with Pedro Tercero. Alba, too, delves into Great-Uncle Marcos' "enchanted trunks" in chapter nine, thus losing herself in his many stories.
In the De Valle family, the members have a great sense of affection and fondness over Marcos.
Severo de Valle views Marcos as a nuisance because he drops in the house from time to time and stay for a long period of time. However, because Marcos is still his brother-in-law and Nivea's sister, he is very lenient towards his actions.
Nivea de Valle is Marcos' sister and is very fond over him. Although she views him as a nuisance, she still loves him dearly and often disregards his actions.
Nana, the nanny, respects him. However, she does not like it when he ruins her pots and pans by making 'formulas' that get stuck on the bottoms of the pans in the end.
Clara de Valle, his niece, is perhaps the most fond of Marcos. She follows him around everywhere the house, read his books, and listen to all his stories. She even helped him when he ran a future telling business. She loves Marcos due to his odd-personality, and how it matched hers. After Marcos passed away, his corpse and belongings (plus a puppy) were delivered to the de Valle family. She even kept the puppy and named it Barrabas.