[にい, nii](n-suf) (1) (fam) used after the name of someone who is an older brother figure; (n) (2) (See お兄さん) used with various honorifics to mean (older) brother#1902[Add to Longdo]
[ねえ, nee](n-suf) (1) (fam) (See 兄・にい) used after the name of someone who is an older sister figure; (n) (2) (See お姉さん) used with various honorifics to mean (older) sister#2721[Add to Longdo]