hi i've been playing this game with my brother. he uses wasd u -grab, i -shield, o -attack, p -special; i use the arrow keys and 0312 for grab, shield, attack and special (in respective order). when i hold the down arrow key and 1 ( attack), my brother cannot move his character. when he holds s (down), I cannot use down arrow key and 1(attack) for down attack. does anyone have a solution to this? thanks.

Try pressing the same button as him. (like, he is pressing S, press down arrow key)

its the keyboard. my school has these. maybe it will be better with controllers, i dunno

This is a hardware issue that pretty much every keyboard has, the specifics vary from keyboard to keyboard. I'm confident that using separate keyboards would fix this issue. Using controllers would also avoid this issue, if you have access to some that can connect to your controller.