Constipated Three yo

My three year old nephew has been having issues pooping for two months. His parents have been giving him suppositories every 3-4 days to help him. They gave his pediatrician lax laxatives for a week. That was three weeks ago. He seems to try pushing but it doesn’t come out. He puts his hands over his bum as if he’s having pain and walks around the house fussing because he can’t push it out. Then he comes to me or my mum to rub his tummy. He looks like he’s going to fall asleep although it’s about 2 hours before his usual bedtime. The last time they gave a laxative he reacted this way but seemed more uncomfortable and fell asleep on my mom’s lap while she was rubbing his tummy. Apparently his parents gave him a suppository too so after 30 minutes of sleeping he woke up screaming and crying and ran downstairs to poop. Screaming and crying the entire time. He is on the spectrum, if that means anything. The parents won’t take him to the doctor. Is there any way to safely help him?