Yes, Arwen is descended from Luthien and so is Aragorn. Elrond is Aragorn's many-times-great-uncle because his brother Elros was the first king of Numenor and Aragorn's ancestor (check this in the Appendices). Elros and Elrond's Mum was Elwing, who was the grand-daughter of Beren and Luthien. So Luthien was Arwen's great-great grandmother.
Anyone ever noticed how inbred they get in Middle-earth? : - )
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