I can't see things that my friend can see

Hello Mojang, I've found a bug in the game. When I played on Creative and Survival mode with my brother, I couldn't see things that my brother can see. I tried fighting mobs at night, but most of them I couldn't see (but my brother can) and got blown up by a creeper I couldn't see . There are some areas that I can't go (like there's a barrier in front of me that is the landscape) but my brother can go to that area (He looked very glitchy when I saw him, but to him he said he looked normal). Please fix this for next update (very excited) and best wishes

-Marcus