Alice is married to Bob, and they have a son named Charlie. Alice's brother, Don, is married to Eva, and they have two daughters, Fiona and Grace. Bob's sister, Hannah, is married to Ian, and they have a son, Jack. What is Fiona's relationship to Jack, and how is Ian related to Charlie?

Respond very briefly.
Fiona is the daughter of Don and Eva. Don is the brother of Alice, who is married to Bob. Hannah, being Bob's sister, is married to Ian, and their son is Jack. Therefore, Fiona is the first cousin of Jack, as their respective parents (Don and Alice for Fiona, Bob and Hannah for Jack) are siblings. Ian is the husband of Hannah, who is Bob's sister, making him Charlie's uncle by marriage. Charlie's father, Bob, is Hannah's brother, so her husband Ian would be the brother-in-law to Bob and the uncle to Bob's son, Charlie.