You mention 'they'. Is there another child in addition to the son with the PDD-spectrum condition? What ages are the children?
Unless there are obstacles that can not be surmounted, such as low income necessitating having persons share a single bed, the sleeping arrangement your describe is not healthy. The children should sleep in their own beds.
yes i have 2 boys ages 10 and 14. the 14 year old has an adhd and odd diagnosis