If anyone in your household uses FB from the IOS or android mobile app from wifi, it will have both your IP address and GPS coordinates. Correlating that multiple people share one residence or workplace is easily done for FB. You can keep playing a shell game like run all your desktop PC traffic through a VPN somewhere so that the FB container doesn't show up as the same geolocation, but you or an ignorant non technical user you live or work with will slip up.
Edit: fb also buys geolocation data from organizations that do the modern equivalent of wardriving. Correlating GPS location with RSSI of specific wifi SSIDs and AP MAC addresses. If anyone near you uses the app, even if their phone has all location services turned off, you're still geoprofiled to within a city block.