I had the same problem as a child. It took me an hour to two hours to get to sleep every night. This persisted until I was an adult, and didn't entirely go away until I had my first child, at which point it disappeared entirely - probably because I was too exhausted from caring for the child, I suspect.
I wouldn't necessarily consider this a problem if it doesn't cause any other problems. Is your child waking up on his own, or at least waking up reasonably refreshed? Is he yawning a lot, feeling sleepy during the day, etc.? Your pediatrician can help you whether your son is sleeping sufficiently overall, certainly, and also is a good person to ask for specific things you can do.
As far as what you can do to help, a few things. My oldest son also takes a while to get to sleep often, and the first thing we did was simply move his bedtime back. He goes to sleep around 9:30-10:00 now, and most days that's sufficient sleep (he gets up around 6:30 on his own accord). It's important to note that he gets less sleep than is recommended for his age, but not dramatically (that's 8.5 to 9 hours sleep, compared to the recommendation of 9 to 12), and it seems to work for him; our pediatrician thinks it's fine, as well. Do discuss this with your pediatrician if you are going to adjust to less than the recommendation so that you can be sure that he's getting sufficient sleep.
This has sometimes made it a bit tough for our younger son (also around 2 years younger), who shares a room like yours does, and seems to need a bit more sleep. During the school year we simply put him to bed earlier than his brother; we often arrange that by having both of them get ready for bed at the 'earlier' time, and then having mom read the younger child books in his bed while dad reads the older child something longer (think a chapter of Harry Potter, takes around an hour to read) downstairs and then come up to bed.
We also allow the older child to read in bed, if he is still not tired (with a small LED bed light that doesn't get hot enough to be dangerous). This is a good option for those days where he's not too exhausted from the day.
Finally, the last thing: make sure your son is doing enough activities during the day that he gets tired - and if so, adjust bedtimes appropriately. Yesterday we biked 10 miles round trip and had an exciting day, and it led to him being more tired this morning - we should've adjusted the bedtime last night back some. Being highly active will help him be tired enough for sleep.