Is a child being afraid of the dark cause by something more?

My 13 year old cousin has been staying with us the past few months and his fear of the dark is starting to really worry me. He will NOT sleep without the ligths on, every night before bed he searches his closet and we even put a lock on the closet door just to reassure him and he can lock it at night. He will go upstairs alone but if he can he will wait for one of us to go up with him. We asked his motehr if he was as scared at home and he  is, they have lived in the same house for 12 years. Nothing really bad that any of us know of has happend to him at night... It makes me wonder if it is caused by his parents issues stressing him out. His father's drinking who is really only around once or twice a month or his mothers drinking and dating new men constantly. Do you think a 12 year old boy being afraid of the dark is just that afraid of the darkness or could it be caused by underlying emotional and/or mental stress? It really is starting to worry me, if it is a sign of something more I do not want to over look it, but I also don't want to be reading too much into something that is perfectly normal.  

[margypops]

I think you hit the nail on the head when you say the home life he has could be affecting him and making him anxious. Yelling and misbehavior at home does affect children, it will stay with him all his life unless it is addressed. Your best bet when he is with you, is not to feed into his behavior, make no issue of it, its okay for him to have a light on at night many children are concerned about the dark.It would be a good idea to talk to his Mom and see if she has some ideas to help him,its also good he has you in his life we all need some caring....