Legolas Greenleaf Long Under Tree - An Essay
Legolas was probably somewhat young, as Elves go. He had never been to Lórien and almost abandoned his journey to Isengard to find out more about the eyes he saw in the "forest" outside of Helm's Deep. Yet, Legolas calls Aragorn and Gimli children. If Legolas has born towards the end of the Watchful Peace, all this might make sense. He would still be young, but would be quite a bit older than Gimli and Aragorn (four hundred and thirteen years older than Gimli and four hundred and seventy years older than Aragorn).
This brings up the question: "Was Legolas Thranduil's heir?" Let's look at the facts: Legolas was sent to Imladris as a messenger, he was allowed to go on a mission in which he could very well be killed, and he brought some of his people to Ithilien (and probably never returned to Mirkwood). With the growing evil in Mirkwood and war brewing in the east, wouldn't the heir of a kingdom stay closer to his people?
Another mystery about Legolas is Celeborn's greeting: "Welcome, son of Thranduil! Too seldom do my kindred journey hither from the North." While this might easily be explained by the fact that all Elves hold themselves akin, rarely do they say my kin. It seems, then, that Legolas is related to the Lord of Lórien, but is it through his mother or father? Almost nothing is said about Legolas's mother, but we are given more information about his father. Thranduil is the son of Oropher, who migrated east from Doriath after its fall. Therefore, we know that Legolas is at least distantly related to Elu Thingol, and in "The Silmarillion" we are told that Celeborn is a "kinsman of Thingol".
By looking at these facts, one might come to the conclusion that Legolas may not have been born any earlier than five hundred years before the War of the Ring, that he might not have been his father's heir (He may have even been his father's youngest child) and that he was akin to Celeborn through his grandfather, Oropher of Doriath. It is also possible that Legolas was at the Battle of the Five Armies. Although all this is no more than educated guessing, it still provides possible solutions to some of the mysteries of Legolas.