Kit got it.
Don't believe about the 2,931 years old thingy. It was just a movie promotional info. But yeah...then again, you could believe it, if we're going on the movies. But in the book, it was never really stated what Legolas' true age is or when was he born. He's the most enigmatic member of the Fellowship. Ironic from the movies, isn't it?
But there are some assumptions that he was born just a little bit after The War of the Last Alliance. But there's also this Legolas of Gondolin, and there was also much confusion if they are one person. Anyway, it's a different story.
And oh, about the Elf that you say looks like him, I assume you're talking about the Elf that have blowing hair? It is not Legolas and it is OFFICIAL. The actor of that character spoke up already and that character that he was playing is a completely original character. There was so much suspicions also when the movie came out that he could be Thranduil, but no, he was just an original Elf character named Fereveldir. Respectively, he was also at the Battle of Helm's Deep. One other thing, if ever it was really Legolas played by Orlando Bloom, we shouldn't even be talking about it anymore because it is certain that it will already be known by almost every fans at this moment if ever. Legolas being very popular and all.
Hope it's cleared up.