Inability to sleep

Hi everyone. i’m looking for some help with getting my boyfriend to sleep normally. He is addicted to video games so his sleep schedule is very bad (goes to bed at 4 and wakes up at 10 for work) i’m worried it’s going to start harming him health wise but i don’t know how to help. he does not want to take sleeping pills or even melatonin for a few reasons so i’m trying to help him find other ways to not be awake all night. Any advice helps!! thanks everyone!