Younger Brother
Little Brother
There is someone wearing horns, holding a bow, and going down a slide held up by a stick. What type of person do you imagine? I'd say someone who's an immature boy. That would be your younger brother.
だい, で, てい
おとうと
None
Your younger brother loves playing dress-up so much that he's now started dyeing (だい) his hair all kinds of colors.