When a Guardian invitation is sent, the recipient may approve the Guardian invitation under a different email address account than the original email address to which the invitation was sent.
This does cause confusion both on the part of parents and guardians and also for schools.
When assessing whether to remove an ACTIVE Guardian, Little SIS will check to see if the email address contained within your SIS export matches either the original invitation email address or the Guardian profile email address.
If a Guardian has accepted an invitation under a different account, you can see this on the Guardian explorer grid alongside the actual email address of the active Guardian profile. (see image below)