Why is the game not showing up in my Family Library?
All of our games are eligible for the Family Library, but in order for them to appear in the family group they must be purchased from the family group and using the family payment method.
For more information you should contact a Google representative since they created the Family Library and its features. You can also find some more details regarding the Family Library in the following Google Play Help URL: https://support.google.com/googleplay/answer/7007852