Luis is the son of Alberto and Sofia. Since Alberto is Maria's brother, and Maria is Jose's wife, Alberto is Jose's brother-in-law. This makes Luis Jose's nephew because Luis is the child of Jose's brother-in-law. In relation to Carlos, Luis is his first cousin because their parents (Maria and Alberto) are siblings.

Ana is the daughter of Alberto and Sofia, making her Luis's sister. Since Ana's father, Alberto, is Maria's brother, Ana is Maria's niece and therefore, Jose's niece by marriage. For Carlos, Ana is his first cousin as their parents are siblings. Ana is not Carlos's mother; Carlos's mother is Maria, as stated in the question.
Jose is married to Maria, and they have a son named Carlos. Maria has a brother named Alberto who is married to Sofia. Alberto and Sofia have two children, a son named Luis and a daughter named Ana. Explain how Luis and Ana are related to Jose and Carlos. Also, is Ana Carlos's mother? Respond very briefly.