Younger Brother, Little Brother
noun
The kanji and the word are exactly the same. That means they share meanings as well.
おとうと
Since this word is made up of a single kanji, it should use the kun'yomi reading. When learning the kanji, you didn't learn that reading, so here's a mnemonic to help you with this word: You look at your younger brother. He's a scheming one. He's smiling up at you. Why? Because he's lit a firecracker on your foot. It explodes, sending your toe flying. You yell "OH. Toe? TOE!" (おとうと) as you realize what's going on.
左の男の子がわたしの弟です。
The boy on the left is my brother.
弟は、テレビを見ません。
My brother doesn't watch TV.
弟と兄は声がそっくりです。
My younger brother and my older brother sound exactly the same.