Eärwen is a daughter of Olwë, wife of Finarfin, and mother of Galadriel, Finrod, Angrod, and Aegnor. She stayed in Aman after the flight of the Ñoldor. She is said to be friends with Anairë, Fingolfin's wife. She presumably still lives with Finarfin.
Her name means "Sea-maiden".
In the family tree of Elwë in the Silmarillion, Eärwen is given as the only child of Olwë, but in the 60th page it states her having brothers, whose names are unknown. It is possible that Eärwen could have unrecorded brothers and sisters, and that Olwë had several children as opposed to only one.