Home Sharing - Allowing family members to stream my music whilst on the same network

Hi. I have a music library on my Mac (iMac (Retina 5K, 27-inch, 2019) running Monterey 12.2.1). I am logged in to my Mac with my Appleid.

Whilst in the house (and on the same network) my son would like to stream music from my library (he is using an iphone 11 with ios 15.3.1). He is logged in to his iphone with his Appleid.

He is named as part of my family (for family sharing)

In the Music app on his phone, he cannot see the library on my Mac in Home Sharing. He can however see my iTunes Store purchases.

My question is, should my son be able to see the full library on my Mac or is it restricted to purchases only?

If it should be the full library, which is the likely setting I have missed.

Please note that I can stream the full library - not just purchases - across the network from my Mac to my iphone (logged in with the same Appleid to both devices).

All help gratefully received.

TC