I just can’t miss opportunity to share my written guide 
EDIT: See the bottom of that post. Basically you need to disable DHCP server in parents router, add estalbished EoIP interface to main LAN bridges in both your home and parents routers. All devices in both locations will get IP addresses from your home, and route all traffic through your home. Not to mention that if you enable upnp in your home, devices connected in parents house will be able to open ports and show “NAT type: Open” in multiplayer games. It’s like your device won’t be able to tell the difference if your device is at home or parents, because everything is routed through your home router.