if i use family share, can my family see my personal photos that are backed up on my icloud?

No - What is Family Sharing? - Apple Support.

"Family Sharing makes it easy for up to six family members to share App Store, music, movie, TV, and book purchases, subscriptions to Apple services like Apple Music, Apple TV+, Apple News+, and Apple Arcade, and an iCloud storage plan — all without sharing each other's Apple accounts."

I would also like to point out that even if you decide to share iCloud Storage as a family, nobody can see you personal photos. Your personal and private data remains private.

There are some things that you can share if you like. You can share a family calendar, family reminders and you can also have a shared photo album, but all of this would be dependent on each person participating if they choose to do so. But when you share items such as these, your own personal calendar, reminders and photos are not accessible to anybody else in the family.