According to this article by Serenity Caldwell of iMore, there are three ways to share photos to all your family members.
Use the "Family" album that is automatically created if you have Family Sharing turned on.
Create a shared album.
Use the same iCloud account for all family members.
Nevertheless, there doesn't seem to be a way to automatically share all your photos to your family members. You will still need to copy photos into the share album. (Unless you are all using the same iCloud account, which I didn't want to do, since each user already have their own active iCloud accounts.)