My first three boys are 12,10 and 7 so relatively close in ages. We then decided to have Scout who is 6 years younger than my last and I have definately noticed the age gap.
It is not so much with the 7yr old at the moment but give it a few years when he is hitting the pre teen stage and Scout is about 4, wanting someone to play with its not going to happen.
My older two boys only have short stints of playing with him now so this is how I know what I have to look forward too.
Suckers for punishment though we decided to give Scout his own play mate. While I love having him home by himself during the day while the others are at school I dont think he is all that bothered by it, as he is so excited when his brothers get home.
It is harder when they are closer together but in our case I prefer it I think.