Could someone please help me?

Onee-san - older sister
Onii-san - older brother

onee son

onee-san/nee-san means older sister
onii-san/nii-san means older brother

i could be your transulater if 你 want. just send me the word and i'll transulate (internet transulaters are hard to under stand since they come out in kanji.)
but if 你 want an internet transulater here;

link

and the difference between oneesan and oniisan;

oniisan= big brother

oneesan= big sister