Not sleeping through the night?

Try some white noise/gentle nature sounds in the background, it helped me.

Like this one (I know it's for babies but it does the job for me) https://www.youtube.com/watch?v=lWjzv_kyvq0&t=1033...

As stated by others insomnia can be caused by different sources. A good sleep routine helps too (no phone, tv near the bed)

change your username, its annoying and it is probably annoying him so he can't sleep.

Insomnia, the inability to get to sleep or sleep well at night, can be caused by stress, jet lag, a health condition, the medications you take, or even the amount of coffee you drink. Insomnia can also be caused by other sleep disorders or mood disorders such as anxiety and depression.

A suggestion I have is to find things that relax him. Since I have an anxiety disorder, I sometimes have a hard time falling asleep. Things that help me and might help him too are ASMR videos on YouTube, soft music , a warm and cozy bed or atmosphere, a night time routine that makes him sleepy, etc.

He should have a sleep study done

I had the same problem, I now wake once a night 

he can try taking melatonin 10 mg for a short term.

We all wake up during the night as we get older. If it's really disturbing his sleep, he needs to talk to a doctor. He may need a sleep study. If it's sleep apnea, where he stops breathing for a few seconds, that can be life threatening, but it can be treated. 

Good sleep hygiene is very important and there are a few recommendations for your friends. Even if he doesn't have issues falling asleep, the habits before bed can impact someone's overall night of sleep. Staying off of your phone or TV 30 minutes before bedtime and do not eat or drink for at least 1 hour before falling asleep. Keeping the room cooler can help from restlessness associated with being warm and needing to remove sheets or extra layers of clothing. Drinking sleepy-time tea that contains chamomile 1 hour before going to bed can help some people sleep better. Another suggestion would be to limit caffeine intake in the afternoon as that can prevent you from reaching deep sleep. Finally, sticking to sleep schedules that are consistent can preventing night-time wakings and waking up too early. If some of these suggestions don't help, he could try melatonin. Melatonin can be bought over the counter and is mainly used to help people fall asleep but it can aid in staying asleep as well. I would recommend starting at 3mg and try it for a few days before increasing the dose to 5mg. The biggest thing to watch out for is the "melatonin-hangover" aka drowsiness that can occur the next morning as the body adjusts. 

Waking once in the sleep period is normal.

Easy sleeping:

Cool Room, warm blankets.

Breeze in the face. (small fan).

Backrest at 30 degree angle (sitting up, easier to breathe) Hospital recommended reduce chances of phenomena.

Radio or other noise maker to cancel ambient noises.

Be tired when going to bed. Don't Do an inventory while relaxing.  I listen to boring old time radio mysteries.

A sleepcast (I recommend Headspace) or some soothing noises like rain, or soft train noises