Well, Maranwe was teasing her and Luthien ran with it. But Luthien is Melian's daughter, and Melian was in the service of Irmo who is Namo's brother in the Thought of Iluvatar. In Fiondil's "Wars of the Valar", Namo treated Melian very much as a younger sister. So it didn't seem out of the bounds of possibility that Luthien might be considered Namo's niece or grandniece, LOL.

*hugs Erulisse* Thank you so much, nettenya. I'm so glad you like it!

Thank you so much! Yes, it's the only one I could think to fit. I used the logic that: Namo and Irmo are brothers in Iluvatar's Thought; Melian/Melyanna was Irmo's servant, and in the original conception of Tolkien's legendarium he thought of the Maiar as the Valar's actual children; so by that logic, Namo could be viewed as Melian's uncle and Luthien's great-uncle. I think even with the changes Tolkien later made, the Valar treated the Maiar very much as either younger siblings or children, in anticipation of the Children to come. So Maranwe isn't too off base in calling Luthien Namo's niece, even teasingly :)