Brothers, Siblings
noun
You have an older brother and a younger brother. Wow! Both are here. These are brothers!
きょうだい
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
あの二人は兄弟です。
Those two are brothers.
マリオとルイージって兄弟だったの!?
Were Mario and Luigi brothers!?
わたしには兄弟が四人います。
I have four siblings.