If Thomas is Joseph's son and Joseph has a brother named Charles who is married to Diana, what is Diana's relationship to Thomas? Also, if Diana has a brother named Andrew, what would Andrew's relationship to Joseph be? Respond very briefly.
Diana is married to Charles, who is the brother of Joseph. Since Joseph is Thomas's father, this means Charles is Thomas's uncle through his father's side. Therefore, Diana, being Charles's wife, is Thomas's aunt by marriage.

Andrew is Diana's brother. Since Diana is married to Charles, Andrew becomes Charles's brother-in-law. Joseph, being Charles's brother, would be Andrew's brother-in-law as well since Andrew's sister Diana is married into the family. Andrew is not related by blood to Joseph, but by the marital connection between Diana and Charles.