Multiplayer gaming (on wifi) keeps on suffocating the person who joins the person who created the world

When I as the host played a game I told my brother to come and play on the iphone 4S, when he joined my server (on wifi) he started suffocated and went back to normal. But then as I realised he was walking underneath blocks when I looked on my iPad 4 then he started suffocating again. Help Me!

Seed was: hunter - no capitals and no spaces ect.