Confused by boys riding boys

Hello group-I come to you with behavioral concerns exhibited by 1 of my now yearling males, Xanti. I brought him home right after being weaned, at about 6 months old. He began life on our farm with a companion he weaned with at his original home farm and a weanling of mine. Everyone settled in and lived this way for several weeks.

As it became time to move the female to my girl-herd, I introduced a then yearling male to this little herd. The older boy is very laid back so all was great. In fact, this young guy & the older one showed at a show in the fall, so it worked out well for them to be pasture buddies.

About 6 months later, thing began changing. The older boy moved back with the older guys (guys his age so he could rough house), and this left my 2 young boys in their pasture. They seemed to be fine, other than Xanti seeming to beg (by humming) to get with the larger herd of boys. (4 boys, 2 intact brothers now 2 and 2 geldings, 1 - 10 & 1 - 7)

I decided to try to allow them to be together. Everything was fine, the old gelding is head of the herd, keeping peace when the brothers get to rowdy. As time went on, however, I noticed the youngsters acting very submissive with tails curled & heads lowered. I thought it was an intact being a bully. WRONG! The 7 yr old gelding has become VERY dominant over these 2. I watched as Xanti acts as if he wants to nurse one of the intacts, & to my horror, this guy mounts him & forces him to the ground. Needless to say, the yearlings are back in their own pasture again.

They still show submission through the fence to all the males in the pastures next to them, but at least I don't have to worry about Xanti (and it's only Xanti) being ridden.

Or at least I thought! This morning we went out to treat what looks to be a "skin condition" beginning on Xanti's legs...I have to wonder, though, as I treat them & look at them more closely. No infection, no swelling, just scabs. Then later I see what just may be the cause...Xanti is again being harrassed, this time by his yearling pasture-mate...being ridden (but unable to be pushed to the ground) and being bitten on the legs I assume to get him to cush. Now, I know boys will be boys, & the fighting is a normal thing, and mounting may be as well, but this appears more than just "practice" I think...

So---sorry for the long lead-up. What I wonder:

1. why does this guy seem to be so overly submissive? He is smaller for his age, but not THAT much smaller...

2. why do I witness him look like he is asking to nurse then the other guy orgling & mounting?

3. do I stop this bahavior, & if so, how? Even the geldings are non-accepting of him...almost like he is instigating their behavior...

and 4. can this behavior possibly cause this guy to be an overly assertive breeding herdsire once he gets to that age? I already have 1 male who doesn't play well with others...don't need another!!

Words of wisdom are welcome!!

Thanks, Lisa