[GreatWarg]

Where did it say Thranduil dwelt with Thingol and Melian? I do not remember reading that. In fact, I believed Thranduil was still young when Oropher (his father) was in the Last Alliance. (Or am I wrong about that?) I also believed that Elrond was older than Legolas. Elrond was born in the First Age, before the third and last Kinslaying and the defeat of Morgoth. I mean, please, Elrond and Elros were taken captive by the Sons of Feanor! It does say somewhere the exact year of Elrond's birth in the Silmarillion.

Legolas Greenleaf of Mirkwood was a different Legolas from the one in Gondolin. Elves often re-use names, and Numenorean names also were Elvish. Such as Denethor the Elf-lord who was killed by Morgoth's forces in the First Age, and the Denethor the Steward of Gondor. There is also a Haldir whom was a Lord of Men in the First Age. I do not think Tolkien made a mistake in re-using these names, but he might have been pointing out that Men and Elves once held themselves akin when Man wandered into Beleriand.