Apple

If you check Settings/AppleID/Family Sharing/ and tap on one of the Family members, can you see, that this member has access to Apple Music?

Did the other members have their own Apple Music subscription prior to you inviting them to Apple Music?

In that case, their individual Apple Music plan should be automatically cancelled.

You might have to contact the official Apple Support and ask them to look into your personal settings.

Start by using this link:

Get Apple Music Support

Or give them a call:

Contact Apple for support and service - Apple Support

Did you as the family organizer change to an Apple Music family subscription?

Get an Apple Music family subscription - Apple Support