Who is The Older Brother from The Lover and what is their importance?

Older brother, born in 1914, is described as violent, sadistic, cunning, and tyrannical. He is also said to be his mother's favorite. Though he was sent to French Indochina to continue his education, Older Brother, spent the money intended to better his life on alcohol and gambling..... when the money ran out he turned to petty crime. Older brother also made a living being a pimp.