None of us are sleeping.

Hi everyone!.

im new to the forum and am posting on behalf of my sister.

my nephew is autistic and bangs his head on his mattress in the night during his sleep. The noise is so loud that he wakes my sister and her husband up and also my nephew not surprisingly suffers with headaches the next day. 
Gp has said he will grow out of it but it is effecting his sleep and he is also epileptic so sleep is important to him. 
they can’t relax because they are worried he will hurt himself and all of them are just trying exhausted. 
we were wondering if anyone has experienced this behaviour and if there’s light at the end of the tunnel or if there’s any tips for a better nights sleep for them all. 
Any advice will be greatly appreciated