Autistic son

Hello, I would like to ask for some advise and support with my son who is undergoing a diagnosis he is 3. My partner has a 4 year old son and we currently have them every other week, we are struggling with my son's sleeping as he does not sleep well at night and is waking her son we have tried changing rooms and sleeping in the same room. My son has had medicine to help but it hasn't helped at all also changed his bed times to later to get him to sleep longer but he still wakes during the night, and any other information about how to support an autistic child would be much appreciated.

Any help or suggestions would be great.

Many thanks