I got 2 call schedules and used up my whole morning and finally get my problem solved. Just want to let people in the same situation as mine know how to resolve this problem.
My father is using Android phone while I'm using Apple device. I received his invitation email "XXX has invited you to Apple Music and Family Sharing" and I clicked the "Get Started", it jumped to safari and opened an iCloud page showing the instruction of accepting the invitation but there was nothing to click for...
What I did was sign out my Apple ID on my Apple device and log in my father's Apple ID on my Apple device. With my father's Apple ID, I invited myself into the Family Sharing. (If using Android Apple Music App, we will receive invitation of Apple Music and Family Sharing together. I do not know why but it just worked if we join the Family Sharing first than Apple Music). Therefore, I successfully joined the Family Sharing and Apple Music membership automatically accessible.
Btw, need to thanks one of the Apple Advisor told me that we need to join the Family Sharing before we can share the membership. Other than that, I'm not sure if Android Apple Music App able to invite family member just to join Family Sharing only, but iPhone yes, that's why I need to use an Apple device to log in to my father's Apple ID (Organizer).
Not sure if I'm just lucky to get the problem resolved but I still hope this helps.
