If a parent has more than one child attending your school and cannot see them all in their Parents App, this is usually due to a missing sibling link or there being duplicate contact ID's in ScholarPack for the parent/carer.
First, check the siblings are all linked in their profiles and have the same contacts. See - Sibling Contact Links
Next, there is an area of ScholarPack called 'Manage Duplicate Contacts' where the system lists potential duplicates for you to match and merge.
Please refer to our guidance - Managing Duplicate Student Contacts for two ways for you to manage duplicate contacts.
See also - How to add contact's to a student profile