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Backup your data to memory stick, external hard drive etc.
Use a strong password to secure your router.
Set up MAC address filtering
Hide the SSID
Format PC's/Laptops and reinstall Operating System and Applications (Maybe consider an opensource O/S such as Ubuntu or Linux Mint..)
Install Antivirus Software/Firewall/Spyware Cleaning software or a security suite e.g. Avast, Zonealarm, Norton, Comodo, Spybot etc.
Install and run Malwarebytes software and upload a log post reinstallation
Change all your passwords for web based apps facebook, banking etc.
Ensure that your kids aren't trying to drive you insane!