Tiny Terror Rises again

So, I think Roscoe is going through another phase. The "Its always rough house play time" phase is not great for humans. My sister fed the horses for us last night and ran into the same issue I did. Roscoe refused to let her leave and tried to play with her by rearing. She did get away with the help of canine distraction.
Today mom and I decided he needed work. I put the bareback pad on DaVinci and mom brought the Brat out to the arena. Ponying lesson #2.
He decided that DaVinci and I made really good moving targets. I had to multitask: ride DaVinci, direct them both, and beat off the baby. Have I mentioned that DaVinci is worth his weight in gold? All during the Roscoe attacks he just kept walking and listening to me. Occasionally he would give a good swish of his tail and tell Roscoe to behave.
After Roscoe nearly pulled me off, we tied the leadline around DaVinci's neck. I also picked up a short whip to keep him off of us both. That worked great for a while. Then Roscoe would hang back and try to rear up onto DaVinci. Thank goodness I do a lot of riding bareback, because he tested all my skills. We did get some peaceful moments and ended the lesson there.
Then he tried to pull the rotten pony routine on mom as she was leading him. Ha, jokes on him. Mom chased his butt around. All the way back to the barn, mom had to move him around. I swear that sweet face hides a devious mind.
DaVinci got a big carrot for his patience and cooperation. Roscoe not worried at all over his activities, cocked a leg in his stall and went to sleep.
We are hoping this behavior is just 8 month old testing us and not hormones starting to show. Any ideas?