Document any and all actions he takes. Fully document. Best way is audio/video evidence. Date/Time recorded. Get as many incidents as you can, then take your Documentation to the Police Department. File a formal complaint for Domestic Harassment. Request a Restraining Order be served on him/his parents. That he/they can not come within 100 feet of you/your family/your property. That 100 foot requirement starts at the beginning of your Property, not your front door.
Take your Documentation to the Mayor's Office and make them aware of the situation. Then take it to the City Council and alert them as well.
IF, after all this, nothing is done, take your Documentation to the local TV Station/Newspaper/Facebook, and or YouTube...….. Basically, make him and his family "famous." A lot of City/County/States have Laws against Domestic Terrorism. The age of the offender is not relevant, other than the fact that the Officials are too lazy or unconcerned with enforcing the Law.
If this becomes a reality, then make them "famous" also. Be sure to Document all your interactions with the Police/Mayor's Office/City Council persons. Document everything! Leave no room for doubt or question.
As well, if he causes any "real property damage," you can file Criminal Charges against him, and Civil Suit against his parents.
Now, all of this is the proper way to do things.
However, if it were me, I would confront the little fart, and then have a special word with his father, and while I may have to be bailed out by someone, I assure you both he and his parents would fully understand my feelings.
Now and again, a little butt kicking is the only thing that works.
Or, you could just move!
Anyhoo.....… bullies are cowards, and if you stand up to them/confront them, they usually fold rather quickly. If this is happening at School to your kids, be sure to Document that, and then speak with the School Administrators, and if they fail to resolve the issue, you can sue them for failing to protect your child/children.
Every ounce of old Soldier in me screams kick the little twerps butt!
You do as you feel led to do.