Robert is married to Maria, and they have a son named Carlos. Maria has two brothers, Alejandro and Luis. Alejandro is married to Sofia, and they have two children, a daughter named Isabela and a son named Miguel. Explain how Sofia and Miguel might be related to Robert and Carlos, respectively. Also, is Luis the uncle of Isabela? Provide a very brief response.
Sofia is married to Alejandro, who is Maria's brother. This makes Sofia Maria's sister-in-law. In relation to Robert, since Maria is his wife, her siblings' spouses are also his in-laws. Therefore, Sofia is Robert's sister-in-law.

Miguel is the son of Alejandro and Sofia. Alejandro is Maria's brother, making Miguel her nephew. Since Maria is Robert's wife, her nephew Miguel is also Robert's nephew through marriage. In relation to Carlos, Miguel is his cousin because their parents, Alejandro and Maria, are siblings.

Luis is the uncle of Isabela. Luis and Alejandro are brothers, and Alejandro is Isabela's father. That sibling relationship between Luis and Alejandro makes Luis the uncle of Alejandro's children, including Isabela.