Alice is married to Bob, which makes Bob Alice's spouse. Claire is Alice's sister, and Dennis is Claire's husband, making Dennis Alice's brother-in-law. Emily is the daughter of Claire and Dennis, and since Claire is Alice's sister, that makes Emily Alice's niece. Because Emily is Alice's niece and Bob is married to Alice, Emily is also related to Bob. The relationship is one by marriage rather than by blood. Therefore, Emily would be Bob's niece by marriage, often simply referred to as his niece.
Alice and Bob are married. Alice's sister, Claire, is married to Dennis. Emily is Claire and Dennis's daughter, making her Alice's niece. Is Emily also related to Bob, and if so, how?

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