Koha has the ability to link patrons. This type of linking is for financial responsibility over materials and fines. An example of these linked relationships are parent-child, organization-employee, and others. These relationships are called Guarantors and Guarantees.
Patron Categories
In Koha, there are specific Patron Category types that can be linked to each other. The patron category type: Adult can be linked via a Guarantee/Guarantor relationship to a Child.
When creating a new patron category, a category type must be associated with it. The options are Adult, Child, Organizational, Professional, Statistical, and Staff. Any Adult Category can be set up to allow for guarantees. This relationship will work similarly to a Child/Adult relationship in Koha.
To update an Adult Patron Category to allow to be a guarantee, go into the Administration module and go to Patron Categories. On the patron category the library would like to edit, go to the far right and click edit. There is a new option found on this form,
"Can be Guarantee" - Yes/No
Adding a Guarantee to a Guarantor
When either an Organizational or Adult patron category type is created in Koha, the option will appear to "Add Guarantee" will appear on the Patron Page. If the guarantee doesn't already exist in the system, library staff will choose to create a new account to be linked to this Guarantor. Once "Add Guarantee" is chosen, then a full patron form will appear and the guarantee information will need to be filled out.
In the Guarantor Box, the linkage between the Guarantor will appear, and the "relationship" can be chosen. This setup is discussed later in the blog post.
There is also the option at this point to add another guarantor to this Guarantee record. The button, "Search to Add" will allow library staff to search in Koha for another guarantor to be linked to the guarantee account that is being created.
Adding Guarantor to Guarantee
If a guarantee is already in the system, and the library would like to link this existing guarantee to a guarantor. Editing the patron record, the "Search to Add" option will appear here. The only guarantors that will appear in this search will be Adult patron category types.
System Preference
The values in this dropdown come from the system preference, borrowerrelationships. The options that are added into this system preference will appear in the dropdown. If a pipe | is added in front of the values, then there can be an option for "not defined". A library can include other choices within the borrowerrelationship system preference. Adding more choices in this system preference will show up in the relationship dropdown.
Requiring a Guarantor for a Child Account
Libraries can require a child patron to link that patron as a guarantor. The child patron account won't be created unless staff link the account to a guarantor from within the Koha database or a person within the Non-Patron Guarantor. The system preference, ChildNeedsGuarantor, will need to be turned on for this process to become effective.

If a library turns this on, any Child patron account that currently does not have a guarantor will need one if that account is edited in any way.
How Fines work with Patron Relationships
When linking patrons within Koha, there are a few system preferences that come in handy on how you want Koha to handle the fines. The first system preference, NoIssuesChargeGuarantees, allows for a library to define an amount of owed money by the guarantee to prevent a checkout to the patron.

System Preference: NoIssuesChargeGuarantees
Asks: Prevent a patron from checking out if the patron has guarantees owing in total more than ___ USD in fines.
The second system preference, NoIssuesChargeGuarantorsWithGuarantees, allows for a library to define a dollar amount of owed fees by the family and will prevent more checkouts.

System Preference, NoIssuesChargeGuarantorsWithGuarantees,
Asks: Prevent a patron from checking out if the patron has guarantors and those guarantors’ guarantees owing in total more than ___ (currency) in fines.
Emails to Both Guarantee and Guarantor
Libraries will have the option to copy the guarantor's email when emailing the guarantee notices. The system preference for this is RedirectGuaranteeEmail. This system preference, if enabled, will email both the guarantee and the guarantor. Staff will be able to see the to/from/cc email addresses within the Notices from the patron's account.