Alejandro is married to Juanita, who is Carlos's sister. This makes Alejandro Carlos's brother-in-law. Similarly, Sofia is married to Carlos, making her Juanita's sister-in-law. Therefore, Alejandro and Sofia are both related by marriage to Juanita and Carlos, but they are not directly related to each other; they are the spouses of siblings.

Miguel is the son of Juanita and Alejandro. Diego is the son of Carlos and Sofia. Since Juanita and Carlos are siblings, their children are cousins. Therefore, Miguel and Diego are first cousins to each other.
Juanita and Carlos are siblings. Juanita is married to Alejandro, and they have a son named Miguel. Carlos is married to Sofia, and they have two children, Luisa and Diego. How are Alejandro and Sofia related to each other? What is the relationship between Miguel and Diego? Respond very briefly.