He should set one up for himself. Apple only requires parents to do it for children under 13 and 2021-2008 = 13 which is probably why you don't see a later year.
Create an Apple ID - https://support.apple.com/HT204316
After you set up Family Sharing
Set up Family Sharing - https://support.apple.com/HT201088
invite him. You may also wish to use Ask To Buy
Request and make purchases with Ask to Buy - https://support.apple.com/HT201089 - Family Organizer receives requests by default, but another parent or guardian can be assigned permission.