How can I see someone's location after the turn it on indefinitely
If he's sharing his location with you through Family Sharing/iMessage click on him in messages, then click "details" in the upper right corner. That should show you a little map with his location. Tap that and it will give you a bigger map. If that's not working you may have to have him manually share from from his messages. He'd go to your contact in messages and then click "share my location" then pick one of the options.