Inbreeding... and a little incest

[Formendacil]

Originally Posted by Selmo

Formendacil calls Elwë, Olwë, and Elmo, brothers. Were they true brothers, in the sense that they were born of the same parents? Or were they amongst the first Elves, created not born? In that case, they may not share the same genes but be called brothers through alliance and affection.
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They are true brothers. Tolkien never once directly states that they were among the first Elves born, while he definitely states that they were brothers (Elmo is specifically said to the younger brother, among other things, a fact that is not likely if they awoke). Furthermore, the shared silver hair of Elwë, Olwë's daughter Eärwen, Elmo's grandson Celeborn (and possibly some others unknown), which is only found among these Elves- and their said-to-be kinsman, Círdan.