I would call this annoying puppy behavior rather than outright aggression. Some puppies are more prone to this type of wrestling and sparring, drive by leg biting. My younger boy Teddy is a wrestler.
First, give all of your other dogs a place to escape the puppy. For us, our older Max was able to jump up on the couch and Teddy could not follow. Your situation will probably require you to physically separate the young puppy from the pack.
Second, work on basic obedience training with the puppy. If possible, work with the whole group together. When my boys get out of hand wrestling, I correct them and redirect them to performing a few tricks for a small treat reward (s single kibble for each trick). Redirecting to playing fetch also helped.
Work on corrections. I used "no bite" when Teddy was a pup. We still use "settle down" or "that's enough."
Walking together and generally wearing out the puppy with activity also helped us reduce the tendency to want to wrestle.
Keep at it and it will improve dramatically with maturity.
__________________ Kristin, Max and Teddy  |