@AR1982 

In addition to setting up parental controls in the router, you can also change the router WAN DNS servers (Log into router using web browser > Advanced > Network > Internet, click Advance) to filter adult content like OpenDNS. 

If the phone uses a VPN connection that will bypass any filtering done by the router.

@Tony thank you for your reply. I will try out what you said. I don't think his phone uses any vpn. But if he were would that be an app he used or in the phones settings?