As salamu alaykum,
This is sadly a common problem in today’s society. Children are often connected to devices instead of connected to people. The problem, as well as the answer is quite simple. His parents need to “disconnect” him from these devices! A five year old should not be on a device 24-7. An hour a day at most for fun, learning or some other useful activity I can see, but other than that, no. Perhaps you can suggest to your brother that he and his wife are the only ones who have control over their child’s usage of these devices. It is the parents who are calling the shots, not the child. Or at least that is how it is supposed to be. You may want to point out (after an educational search on the negative effects of children & devices) how harmful it is to their child’s development to let him isolate in another virtual world. I would kindly suggest to him that the time his child is spending using all these devices should be stopped and replaced with real life experiences and people. Insha’Allah, your brother will heed your advice and unplug his son. We wish you the best, please let us know how it turns out.