Juan is Carlos' son, and Carlos has a brother named Alberto. Alberto has two children, a son named Eduardo and a daughter named Sofia. Juan got married to Luisa and had a daughter named Isabela. How are Eduardo and Sofia related to Isabela, and what is Luisa's relationship to Carlos?
Provide a very short response.
Eduardo and Sofia are the children of Alberto, who is the brother of Carlos, making them Carlos' nephew and niece, respectively. Since Juan is Carlos' son, this makes Eduardo and Sofia the first cousins of Juan. Isabela, being the daughter of Juan, is Eduardo and Sofia's first cousin once removed because she is one generation below them.

Luisa is Juan's wife, which makes her Carlos' daughter-in-law, as she is married to Carlos' son.