*兄 (ani) - older brother
*姉 (ane) - older sister
Younger sibling:
*弟 (otoutou) - younger brother
*妹 (imouto) - younger sister
Other terms:
*兄弟 (kyoudai) - siblings (male or female)
*姉妹 (shimai) - sisters
*兄弟姉妹 (kyoudai shimai) - siblings (male and female)