Same with oji (uncle)/oba (aunt):
叔父: uncle (younger than one's parent)
伯父: uncle (older than one's parent)
叔母: aunt (younger than one's parent)
伯母: aunt (older than one's parent)
Oh wow, I didn't know that one! Thanks!
叔父: uncle (younger than one's parent)
伯父: uncle (older than one's parent)
叔母: aunt (younger than one's parent)
伯母: aunt (older than one's parent)
兄弟：Elder brother, younger brother
姉弟：Elder sister, younger brother
兄妹：Elder brother, younger sister
The 4th remaining case is 姉妹, and is read "shimai".