Why does my kitten never leave my older cat alone?

i have a bengal which is nine years old, male and a kitten on 6 months, male, which is a ragdoll. My ragdoll never leaves my bengal alone. He will follow him and continue to jump on him, bite his tail, till i shut them in separate rooms because he never stops. When my cat is sleeping the kitten wakes him up by biting his ear, till my cats runs away outside to go somewhere else. My bengal had turned aggressive towards me he used to be calm and loving but if i go near him all he does is growl and hiss at me and seems never happy. How can i stop the kitten pestering him, i cant keep them apart for ever.My bengal seems depressed and upset all the time and its horrible to see this happen, my ragdoll is almost as big as him now and runs in front of him and doesn't let him go in and out a room. my bengal once flipped at the kitten and started biting its neck, i swear that means hes trying to kill him like they do with their pray, please help