how do i see subscriptions made by my family members under apple one

Apple One is a subscription that includes various services. You cannot subscribe to things under it beyond those it includes.

If you mean subscriptions your family group members have outside of Apple One, you would need to check their accounts in their devices.

Any subscriptions they may have that are also included in Apple One, will get cancelled automatically once the Apple One free trial ends.

The only exception is iCloud, if their personal subscription has more storage than the amount offered with Apple One. In which case it will not get cancelled. They must then choose to cancel it themselves.