itunes and iphone not syncing

Welcome to Apple Support Communities Schniguy,

We can see you've been using Download and use iTunes for Windows, and you've found that you're unable to sync your iPhone to your PC since joining Family Sharing.

We're glad that you were able to join your nephew's family plan. If it includes Apple Music, syncing music through iTunes might be turned off. It's described in this guide: Use iTunes to sync your iPhone, iPad, or iPod with your computer. We'd also suggest looking through this guide to double check your sync settings. You might even want to set it up once again, then see if it syncs for you.

Kind regards.

Schniguy,

You didn't mention whether you're using Apple Music, but it sounds like you have it. If so, the sync options wouldn't be there because it's syncing through iCloud. You might find this discussion helpful: No 'sync music' check box & all music… - Apple Community. We're sharing it because it does describe what you're seeing and it has been recommended by Apple.

Take care!