A 5 year old boy has been sleeping at night in the same bed as his single mother for basically his whole life, although he has his own bedroom and his own bed. They go to sleep together at the boy's bedtime and the mom gets up after the child is asleep (sometimes). Is a boy this age sleeping with his mom common? At what age should it stop? (Yes, this is a relative.)
There is exactly one age when this should stop:
When one of the individuals concerned is no longer happy with the sleeping arrangements.
Assuming that your real question is somewhere along the lines of "Is this going to mess with the development of the five yo., sexually or otherwise?" - No, he will be fine.
I can reference my own experience here:
Our 5-year sleeps on our bed. He goes to be in his own bed, and gets up and moved to our bed in the middle of the night. He is turning 5 shortly, and recently he has had nights where he doesn't go to our bed. Most nights he sleeps in our bed.
We made the decision to neither encourage nor discourage co-sleeping with our kids. We put them to bed in their own beds, but if they want to move into our bed they can. There are many reason for this, and many of them are practical.
I have noticed that among other parents of toddlers and pre-schoolers, IF you practice co-sleeping, many kids are still in their parents bed at this age.
My husband and I did a lot of research a few years ago. We now have an 8 yr old boy and 5 yr old girl. We had the hardest time with our boy because when he was at his real mother's house, he always slept with his mother or one of his older brothers, being the youngest of 5 boys there. I initially had a hard time with this being my relationship with his dad started the same time he was born. Then, when my daughter was born, I breastfed for a while and we researched more about cosleeping for fear of smothering our newborn. All the research I remember showed that, generally, there is no longer term damage to the child psychologically. In many indigenous communities in places like Malaysia, entire families sleep together, including grandparents. But the one thing that always stuck out to me was my husband saying, "Do you really think either of them are still going to want to sleep with us when they're teenagers? Enjoy it while you can." Hope this helps.
I believe a lot depends on the boy, and hopefully the mother knows her son. At about the same age as this boy, and for a couple of years after I tried my best to see my mother in various states of undress, and would try to find ways to see her naked. At times I would crawl into bed with her when my dad got up early, and then would get as close to her as possible and "accidently" touch her woman parts. On the other hand, my brother never had any interest in her what so ever even though they were much closer emotionally than mom and I were. So, that's why I say it depends a lot on the son and what the mother knows about him. No one size fits all. And further, no I did not grow up weird, and I wasn't a terror to my girlfriends nor to my own daughters.
I think it really depends on the situation. If the mom and kid are by themselves (no father present) then it probably makes more sense that they would sleep in the same bed. I'm sure there will come a day fairly soon where that will no longer be the case. I really don't think its a big deal at this point in time.
As parents of two boys(6 & 4), my wife and I tuck them into bed every night. Some nights (maybe once every 2-3 weeks) one of the boys ends up in our bedroom for a variety of reasons: cold/hot, couldn't sleep, scared of some noise or the weather, etc. When that happens, we usually let them stay for a little while until they fall asleep and then tuck them back in their own bed. I will also add that when our boys do come into our bed, they almost always sleep on my wife's side of the bed.