First of all, try to stop yelling. It's incredibly hard, I know, but as my friend says, "You don't have to go to every fight you're invited to." You are the boss and you have to have the confidence that you are. It's so easy to get frustrated but you need to be consistent and firm, and not engage in giving him the attention he is demanding. Even negative attention is attention.
Secondly, "just brothers" or "boys being boys" is a slippery slope - it allows behavior in boys that we would not tolerate in girls. It creates a level of permission for them to engage in certain behaviors. Remove him from the situation and put him in his room. If he won't sit in a time out corner or time out chair, then put him someplace secure. I put a little gate hook on my son's door so he had to stay in there. If he trashed the place, then we removed everything from the room - all the toys etc. - and put them in the attic. We left books and his stuffed animals for security, but no luxuries.
Whatever your son values most, you take away every time he behaves this way. If you are out someplace, you leave and go home. As inconvenient as it can be, it only takes a few episodes. My son went through a head-butting stage, whacking his head into others kids or even me. I have left restaurants and left supermarkets with a half-filled cart - I just told the manager I needed to remove my son from the store and I was sorry but could someone put the groceries back on the shelves. My son couldn't believe it - but I only had to do it 3 times.
Give all the attention to the younger brother if the older one is being difficult. He goes in his room, and you and the younger one will play until the older can behave. And vice versa, if the little one starts up with this. Don't engage in the argument, just state the facts ("We don't hit in this house." "No biting.") and move on. He doesn't have to understand the reasons right now - he just has to stop.
A good rule is that things are only funny if both people are having fun. If one person thinks it's a riot but the other one is crying or angry, then it isn't fun. It goes for verbal comments, jokes, ridicule, etc. as well as physical stuff. I think, given the age and size difference between your kids, it's inevitable that any type of wrestling match is not going to be fun or harmless for very long.
I think rechanneling excess energy, as one poster suggested, is fine. Kids need to learn to self-regulate and to get rid of aggression in positive ways. Teaching a kid to run laps or even punch a pillow (as long as it never gets to punching a pet or a wall) is okay. It's a good skill for later on.
Good luck - it's frustrating but you will be glad that you took charge early in their lives.