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 आप 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 आप want an internet transulater here;

link

and the difference between oneesan and oniisan;

oniisan= big brother

oneesan= big sister