The biggest littlun is Henry.
He is a littlun and is a minor character in the book
In The Lord of the Flies Simon cares for and gets along well with the Littluns. He takes the time to care for the Littluns.
He sees a snake beastie thing in the jungle.
In "Lord of the Flies," the beast is said to inhabit the jungle during the day. The littlun describes it as a creature that hides in the treetops and comes out at night.
The littlun Phil held the conch and spoke quite confidently about seeing something 'big and horrid' moving among the trees. The littlun Percival burst into tears and eventually Piggy and then Jack had to relate aloud to the rest of the boys what he was saying.
The first little'un to go missing is the boy with the mulberry coloured birthmark and he goes missing during the time that the fire is out of control on top of the mountain, in chapter 2.
The first boy who appears after the conch is blown is "Johnny". From description, he appears to be one of the littlun's.
In "Lord of the Flies," the wild boar does not specifically eat the littlun with the mulberry-colored birthmark. Instead, the boy goes missing after the boys' frenzied dance and chant during a hunting ritual, which leads to the assumption that he may have fallen victim to the chaos of their descent into savagery. The boar symbolizes the primal instincts awakening within the boys, but it is the group’s brutality that ultimately contributes to the littlun's fate.
I believe he is 12 because he certainly isn't a "littlun" but is a "biggun" which is about 10-12 years of age or something similar to that.
In Lord of the Flies the littlun with the mulberry coloured birthmark on his face raises two question. Firstly he asks what the boys intend to do about the snake-thing. Secondly he also asks will it return the coming night.
Jack suggests that they could use a littlun as the pig in the game instead. He believes this could serve as a viable alternative to using a real pig for their hunting and violence.
The littlun with the mulberry coloured birthmark on his face was the first boy to mention the snake-thing or beastie. He mentioned it at the meeting in chapter 2: Fire on the Mountain. The littlun he said that he'd seen during the previous night and he was worried that it might return and try to eat him.