Your younger brother: Otoosan (polite)
Your elder brother: oniisan (polite)
otouto
兄 (ani) is older brother in Japanese. When addressing someone else's older brother, you should use お兄さん (onii-san).
You may say 'ani' for older brother, and 'otouto' for younger brother, written (in that order): 兄 弟
if you mean brother its "otosan" that is in polite form <3
You may say something along the lines of "Niichan, konnichiwa."
In Japanese you say onii-sanonii-san is older brother. Nissan (Ni-san) is big brother. However, this is the formal way. For a more relaxed informal way, you delete the san and replace it with a Chan.I.e: Onii-Chan : Older brother
That would be 'Sayonara Nii-san' if they are older. There are many different ways to say older brother, I chose nii-san since I believe it to be the most common. If it is a younger brother one would say 'Sayonara Otouto' Both of these simply read 'Goodbye Brother' because in Japanese words like my are understood.
otouto = younger brother otouto san WA _____ = my younger brother is _____ You call your little brother otouto. If it is a baby you can refer to it as akachan as well, but it seems a little distant.
Lol i love to call my bother Nii-chan (Onii-chan)
'Anta no nii-san WA baka da'.
'Niichan no koto o shimpai shite iru yo.'
'Anata WA ijiwarui ani dattara dou desu ka?'.