Kids of the 21 century are very exposed to sex related videos and vibes. Kids should be allow to know about sex step by step according to their age.
Here are the things you should do in a case of kids touching other kids private parts, prevention and control.
kids touching other kids private parts
Keep the kid away from nudity and any other vulnerable position that will make him think about sex more than normal.
kids touching other kids private parts
Directly scold him, telling him how bad it is to do such a thing. Not because he's a kid and you're in control but it's bad for his growth and developement.
kids touching other kids private parts
Preventing kids from touching other kids private part
Reduce the exposure of the media.
Distract him with games and other activities that will keep the kid busy and his mind working.
Commend him for every improvement with an award of encouragement.
Helping a kid to come out of sexual obsession is a big role you need to play in making that kid a responsible fellow in the future.
Instead of just scolding him, make him do something that motivates his creativity, dreams, which might bring about genuine cultivation.