Family Sharing Apple Music

I have an IPhone 7 Plus. My brother in-law has me on his Family Sharing plan and it clearly shows my name but it just shows I have access to ICloud Storage and some Fitness Plan/App but doesn’t show Apple Music for some reason and I can’t look up any songs without it asking me to pay from my own individual plan. Why is this and how can I fix this where I also will have access to Apple Music with Family Sharing?