My draft number was 322, but I enlisted in the Army at 22 (1974), even though my brother had threaten to shoot me if I enlisted - he did not want me going over. By 74 the threat had worn off, though and I went in anyway, even though I was married and had a one kid and another on the way.
Why was your brother upset, enlisting in 1974 was a safe bet. We got out of Vietnam in April 1973.