Bravo for raising boys that like to spend time together that much. I am a little concerned about the age gap and the fighting, but not knowing your kids, it is hard to say if it is a problem. I agree with J.B. that putting the onus on the older kid is important since it is unlikely that he would get hurt and should also have the better understanding/control over the 7 yr old.
We have 6 kids, in 3 "groupings" (2 are 27/29, 2 are 20, 2 are 16/18), so I've dealt with fighting with kids the same age and kids with pretty big age differences. Over all, unless I am really afraid that someone is going to get hurt, I generally didn't interfere. They had to take it outside, of course, but other than that, I'd try to let them work it out. My experience was that the for the boys, they tended to see it as a solution to some perceived problem - we fight, we get over it, we move on. The girls - well, that was a different story. The fighting was much more emotionally driven and solved nothing . . . ever.
So, if you think that your 11 yr old would "pull his punches" if it really came down to it and your 7 yr old can pretty much hold his own, then I wouldn't get overly invested in it. We did get our boys boxing gloves so at least it seemed like the fighting was more "constructive" rather than just brawling. Often, when a fight would start, I'd holler to get their gloves and get outside, and by the time they did that, the fight was forgotten about, or they would just switch to boxing for fun. The one thing I didn't allow was tattling - the whole he said/he said thing. If they were going to fight, they couldn't complain to me about it or the outcome (obviously if someone was picking on or constantly starting something, that was different, but as a mom I think you know the difference between two kids having it out and one kid always being the bully).
Good luck - and enjoy these years! They might not be close for much longer and in some ways, fighting is the only physical expression some boys think they can show a brother.