Hello Valpal32,
Thank you for reaching out to Apple Support Communities, and we'll be happy to help in any way we can. We understand you're having issues with syncing contacts to your son's iPhone. Does he use iCloud for contacts, or another email account? If he uses iCloud, you can sync them using these steps: Set up iCloud for Contacts on all your devices - Apple Support
"Set up iCloud for Contacts on your iPhone, iPad, or iPod touch
- On your iPhone, iPad, or iPod touch, go to Settings > [your name] > iCloud.
- Do one of the following:
- iOS 16, iPadOS 16, or later: Tap Show All, then turn on Contacts.
- iOS 15, iPadOS 15, or earlier: Turn on Contacts.
- To view contacts stored in iCloud, open the Contacts app, then do one of the following:
- If you have more than one source of contacts: Tap Groups. Below iCloud, select All Contacts or another group.
- If you don’t have multiple contacts sources: All the contacts you see are stored in iCloud.
For more information on how to use Contacts on your iPhone, iPad, or iPod touch, or to use iCloud contacts to manage who your children can communicate with on their Apple devices, see any of the following:
We hope this helps.
Cheers!