Sharing a storage plan doesn't give you any access to his photos that you don't have when not sharing a storage plan -- as stated in the first reply:
When you share a storage plan, your photos and documents stay private and everyone keeps using their own accounts with iCloud—just like when you have your own storage plan. You simply share the space available in the iCloud storage plan with your family members, so you only have one plan to manage.
However, whether or not you share a storage plan, you can share specific photos. See the following from Family Sharing - Apple
When you set up your family, a shared album is created automatically in the Photos app on all family members’ devices. Everyone can add photos, videos, and comments to the album whenever they like and get notified when something new is added.
and also see: How to share albums in Photos on your iPhone, iPad, and Mac - Apple Support