Premise: Amandil is a fictional character from J.R.R. Tolkien's Middle-earth legendarium. Amandil was a Lord of Andúnië, succeeding his father Númendil upon his death. Amandil is most noted for being the father of Elendil, founder of the Númenórean Realms in Exile.
Hypothesis: Elendil is the sister of Amandil.