Lupe is married to Oscar, who is the brother of Juan. Juan is married to Maria, who is Carlos's sister. This makes Lupe Carlos's sister-in-law, as she is the wife of Carlos's brother-in-law. Isabel is the daughter of Maria and Juan, and Hector is the son of Lupe and Oscar. Since Juan and Oscar are brothers, their children Isabel and Hector are first cousins to each other.
Carlos has a sister named Maria. Maria is married to Juan, and they have a daughter named Isabel. Juan's brother, Oscar, is married to Lupe, and they have a son named Hector. How is Lupe related to Carlos, and what is Isabel's relationship to Hector? Make your response very short.