Disclaimer: I do not own any of the characters that appear in The Hobbit or The Lord of the Rings trilogy.
Author's Note: Nothing is known of Legolas' mother;I have assumed that she died in childbirth.
'In a great hall with pillars hewn out of the living stone sat the Elvenking on a chair of carven wood. On his head was a crown of berries and red leaves, for the autumn was come again. In the spring he wore a crown of woodland flowers. In his hand he held a carven staff of oak.' JRR Tolkien, The Hobbit.
"Where are we going Ada?" asked Legolas, scampering along beside his father.
"To the vaults," replied Thranduil, taking his son's little hand and guiding him into a dimly-lit side-passage.
Legolas considered his father's answer. "Ada—what is the vaults?"
"A safe place in which to keep things," replied Thranduil.
"Oh." Legolas frowned. "What sort of things?
"You will see when we get there." The Elvenking hurried down the corridor—making no concessions for the elfling's tiny stride—to a simple doorway cut into the living rock and, with a curt nod to the guards standing either side, ducked under the lintel, pulling Legolas—"Ada is teaching me how to be King!"—behind him.
"Keep a hold of my hand," said Thranduil, "these steps are very steep."
Moving more slowly now, the pair descended to the cellars, then kept going downwards, until the stairs ended in a single narrow corridor, lit by a few scattered torches.
Legolas looked about him. "Is this the dungeons?" he asked.
"What do you know about dungeons?" said Thranduil.
"Gwanur Nerdanel told me that the dungeons are where you keep elflings who have been bad," said Legolas.
"Did she now," said Thranduil. "And had you been bad?"
After many twists and turns, passing several stout wooden doors secured with heavy padlocks—"Is this where you put the naughty elflings, Ada?"—they came to the remains of a doorway, walled up with massive stone blocks. Thranduil removed a torch from the sconce beside the sealed arch, seized the empty bracket, and pulled it downwards. With a deep groan, the false blocking swung away and the Elvenking, holding the light aloft, led Legolas into the vault.
The room was filled with wooden chests, each about the size of Legolas' own toy box, and some—like his toy box—had been crammed too full, so that their lids could not be closed and the elfling could see what lay inside.
Some of the chests held pieces of green—dark, like the rind of a melon, or bright, like new leaves in spring, or pale, like the waters of the forest river—and all of them flashed and sparkled in the torchlight.
Legolas had never seen anything so fascinating.
He slipped from his father's grasp and approached the nearest chest, inclining his head this way and that to make the sparks fly. The other boxes were piled with chunks of red—warm and rich, like his ada's favourite wine—or chips of white—cold, like the ice that had hung from the Great Gates last Yuletide—or pieces of blue—pale, like a fine winter sky.
Legolas took up a handful and let them fall back into the box... "What are these, Ada?"
"Our wealth," said Thranduil.
"Oh." Legolas seized another tiny fistful. "Ada, what—"
"Come over here." Thranduil held out his hand. Legolas dropped the sapphires and toddled, between the chests, to where his father was standing beside a long, narrow box decorated with gold. "Do you recognise this?" asked the Elvenking, pointing to the inlay.
"They are beech leaves, Ada," said Legolas. "And that is your sword."
Thranduil smiled. "These are the arms of the Woodland Realm," he said. "They tell us that there is something important in this box, something that belongs to me as King, and to you as Prince, of this kingdom. Whenever you see this sword,"—he traced it with his finger—"surrounded by these leaves, you must remember your duty as Crown Prince. Do you understand?"
"Good. Now open the chest."
Obediently, Legolas pushed up the heavy lid. Hand-in-hand, father and son gazed down at three elaborate circlets, intricately wrought in silver, and studded with diamonds and pale, watery emeralds.
"Do you know what those are?" asked Thranduil.
"Crowns…" said Legolas.
"The Crown Jewels of the Woodland Realm," said Thranduil. "This one,"—he pointed to the largest—"is the King's; this one, the Queen's; and this,"— he pointed to the smallest—"belongs to the Crown Prince."
"Me," said Legolas.
"But…" The elfling stretched out his free hand and tentatively touched the princely circlet. "This is made of metal, Ada. And a real crown is made of flowers and leaves."
"A real crown…?" Gently, Thranduil drew Legolas' hand from inside the chest and closed the lid. "Come, Lasdithen—let us go outside and I will explain."
The Greenwood was sparkling with light summer rain.
Thranduil led his son through the Great Gates, across the terrace, and lifted him onto the parapet at the side of the stone steps. "Can you see the houses, Legolas? Up in the trees?" The Elvenking pointed, across the Forest River, to various dwellings nestling amongst the branches.
"And do you know who lives in them?"
"Our people—yes—very good. I am their King and you are their Prince. And do you know why kings wear crowns, Lasdithen?"
"So that their people know who they are," said Legolas.
"Very good." Thranduil smiled. "And what is a king? What does he—what do I—do?"
"You work in your study," said Legolas.
"Yes, sometimes. Doing what?"
"Letters?" Thranduil began to suspect that the conversation might be going awry. "What sort of letters?"
"Letters about wine," said Legolas, confidently. "When it tastes like vinegar. And about deerskins, when the Beornings have not paid for them."
"Hmm." The Elvenking wrapped a strong arm around his son. How do I explain this, he wondered, to a child? "A king," he said, "takes care of his people, just as an Ada takes care of his son. A king makes sure that his people have food to eat, and a safe place to sleep, and can live without fear. Sometimes he can do it by talking or by writing letters; sometimes by giving gifts or by making payments; but sometimes he has no choice but to stand up for his people—the way I would stand up for you if somebody threatened you,"—he gave his son a proud little hug—"the way you stood up for Collo when Saelbeth was bullying him.
"That is what a king is. He is his people's Ada."
Legolas nodded, but said nothing.
Thranduil continued. "To be an Ada to so many people, a king must be rich. The jewels you saw in the vault—the green and red and white gems—will buy many bows and arrows to protect them."
The Elvenking frowned—Legolas did not seem as interested as he had expected—but he decided to persevere. "When I am here, in the Palace, I wear a crown of leaves or flowers—a real crown, as you put it,"—he gave the child another little squeeze—"because my people already know that I am their Ada. But when I meet with other kings, I wear a crown of metal—" Thranduil realised that his son's head had begun to droop. "Are you listening, Legolas?"
"Yes," said the elfling, his little lip quivering.
"What is wrong?"
"Do not tell me 'nothing'," said Thranduil. "Tell me what is troubling you." He leant closer—a trifle impatiently—to hear his son's mumbled reply.
"I thought you were just my Ada, not everybody's."
"Oh Little Leaf!"
Thranduil—so seldom openly demonstrative—folded his arms about his tiny son and held him against his chest, rocking him back and forth. "Of course I am your Ada! I am your real Ada—not a pretend Ada, as I am to them!"
He kissed the crown of the child's head. "I love you more than anything in Middle Earth, Legolas Thranduilion," he said.
And though his heart had always known it, it seemed to Thranduil that his mind was only now recognising the truth of it. "No Ada ever loved his elfling more than I love you, my precious, precious son."
Ada … 'daddy'
Lasdithen … 'Little Leaf'
Gwanur … 'Kinswoman' (since there doesn't seem to be a Sindarin word for 'nurse').