Will private pics and ever be shared?I hope not!

Pictures on your phone or in iCloud are private, unless you explicitly share them, or your iCloud account is hacked. To eliminate that as a possibility use a strong unguessable password at least 10 characters long (16 would be better) and implement 2 factor authentication on your account: Two-factor authentication for Apple ID - Apple Support

Having said that, law enforcement agencies may be able to force you to unlock your phone for them. Depends on country and state. And within 150 miles of an international border the border patrol can also force you to.

It's up to you.

If you wish to keep them private, do so.