Parents with multiple children will have multiple user logins despite having the same details.
This is normal and expected behaviour and is caused by the limitations of Integris.
"This is an historical difference with Integris and is expected behaviour when speaking with their engineers.
Unlike other MIS's, Integris doesn't have a student sibling link that would link siblings with the same parents. Each pupil will have their own parent links, who in turn will have their own MIS ID's. When a Sibling is added, they would also have their own parent details and these parents will have their own MIS ID and their own link to the pupil. When Wonde comes in to get this data, we then pull two separate records for the same parent, there's not a way with how their product is built that we can obtain a single ID, their MIS copies the contact data from the source students contact record and overwrites the data in the destination students contact record, it does not link them both to a single record.
Unfortunately we cannot provide a direct solution to this, though I'm aware that applications will have something on their side as a workaround so that they do not have multiple copies of an account in place on their respective products."