I killed my first deer with a Remington 1100 2 3/4 inch 20 guage and #3 buck.
The deer was only ten yards from me. The first shot he didnt hardly break his stride but the second shot put him down. Im sure the first shot would have done the trick but the buck may have ran 50 yards before he fell. Definatly keep the shots no more than 20 or 25 yards. My feeling is if your brother keeps his shots very close it should be sufficient but try to keepem within 20 yards. Bow range.
My second deer was standing a little over 20 yards away. I shot him twice also and he still ran 70 yards before piling up. I then decided that I needed a 12 guage.