Hi verildo,
welcome to this Apple (user-to-user) Community!
Re: "Family Sharing : Add family member stuck on Android"
Apple Support's online article (link below) may help:
Use Family Sharing with Apple Music on Android - Apple Support
Eg Says you can:
"Invite people to join your family group and share your subscription
- On your Android device, open the Apple Music app.
- Tap the More button (the three vertical dots)
- Tap Account.
- Tap Manage Family.
- Tap Add Family Member.
- Enter a name or email address.
- Tap Send.
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For the family members: Above linked article also says:
"Accept an invitation to a family group and share their Apple Music subscription
- Download the Apple Music app from Google Play to your Android device.
- On your Android device, open the email invitation to join Family Sharing.
- Tap the link in the email invitation.
- In the "Open with" screen, tap Apple Music.
- Tap Accept.
- Sign in with your Apple ID and password"
Seems everyone gets their own library in the Music app, to which they can add whatever music they enjoy.