my daughter did this also, she is just getting out of it and she just turned 12. but ours started when we moved to our new house and her room was upstairs. so we just figured it was having her own room for the first time, she used to share in the rent house. and being upstairs.
she also used to have nighmare and sleep walking at this time. i figured it was brought on by stress of having her own room. My mom said i also went thru a period of nightmares and sleep walking. so i wasnt too concerned.
what we did do, is reassure her that she was okay, and nothing cbad could happen. i would often sit up in her room at bedtime and talk about whatever was bothering her mind. one of the things that came up during those talks was she was scared someone could climb on the roof and get in thru her window. after assurance and even taking her to the roof to show her it wouldnt be possible, the nightmares slowly stopped.
but we are talking 4 year time period, during that time, i would just turn off her light after she went to sleep (and after she got up to go to the bathroom) and we got her a nightlight. which worked wonders too. we did end up taking all the bulbs out of the closets (because it was actually burning the wood) but left the room light one.
so my suggestion is get him a nightlight and talk with him before bed. Oh and do the happy thought game which is when they are in bed, talk to them about things that make them happy, ie puppies playing, swimming at the lake, and tell the child to picture that thought, actually go thru a sincerio with him, for instance, can you see yourself playing in the water, what are you wearing, what are you doing, are you laughing, think about trying to catch the tadpoles, based off real life experiences of course so he can actually "picture" it in his head and tell him when he starts getting scarey thoughts to start thinking of the happy thoughts iyou came up with nstead. takes awhile (a year or so with mine) but she does this on her own now.
good luck.
It is uncommon for a 12 year-old to have a fear of the night. When did this start? Did a specific event trigger this, to your knowledge? Is he having any other issues at the moment other than the fear of the night? Regardless, I would suggest you take him to see a child therapist to at least be evaluated.
what exactly is he afraid of? is it that there may be a burglar that comes into the house, a monster or some creature, a fire that may happen, etc.? If you have a security system, remind him of that and that there are smoke detectors in the house as well. If your bedroom is somewhat close to his, remind him of that as well, showing him that you will be there to protect him and that he has nothing to worry about.