Javier has a sister named Isabel. Isabel is married to Carlos, and they have a son named Miguel. Javier is married to Sofia, and they have two children, Ana and Eduardo. Explain how Sofia is related to Miguel and how Miguel is related to Ana. Also, discuss if Carlos is Javier's brother. Provide a very brief response.
Sofia is Miguel's aunt by marriage. This is because Miguel is the son of Isabel, who is the sister of Sofia's husband, Javier. Therefore, Sofia is Isabel's sister-in-law and thus Miguel's aunt through her marriage to Javier.

Miguel is Ana's first cousin. Miguel's father, Carlos, is married to Ana's aunt, Isabel. Isabel is the sister of Ana's father, Javier. This makes Miguel and Ana, children of siblings, hence first cousins.

Carlos is not Javier's brother. Carlos is Isabel's husband, and since Isabel is Javier's sister, that makes Carlos Javier's brother-in-law, not his biological brother.