My boy Ammo had this same problem. It was like he viewed them as litter mates. We tried a lot of things to change it. The only thing that seemed to really help was having my kids turn their back to him and ignore his behavior. He would run up to bite at them and they would immediately turn around. I made them stay where they were so it didn't seem like they were running from him. It only took a couple times and he stopped all together. Since then we have not had to deal with him biting at them. Hope this helps, good luck.
Kolt Ammo Vom Geschenk "Ammo"