Migrate related items

Based on your migration scenario, the Kentico Migration Tool does NOT have out-of-the-box support for migrating KX13 "Related Pages" (named relationships) this is a gap you'll need to handle with a custom approach.

Why Related Items Don't Migrate Automatically

In Kentico 13, "Related pages" use named relationships stored in the CMS_Relationship and CMS_RelationshipName tables. XbyK fundamentally changed this model relationships between content are now expressed as Content item reference fields (typed, structured fields within a content type pointing to other content items) rather than a standalone relational binding table. The Migration Tool's supported data list covers pages, content types, media libraries, contacts, activities, etc., but does not list relationship names or page relationship bindings.

Approach 1: Remap Relationships as Content Item Reference Fields (Recommended)
This is the XbyK-native approach and the best long-term solution:

In your KX13 content type (page type), add a new field of type Content item reference (or a list of references) that will hold the "related items" data.

Approach 2: Migrate via the Universal Migration Tool (UMT) : https://github.com/Kentico/xperience-by-kentico-universal-migration-tool
If your related items scenario is complex (many content types, many relationships), use the Universal Migration Tool (UMT) directly:

Export your KX13 data (pages + relationships) into UMT's JSON import format.

Before feeding each content item to UMT, resolve its related items from CMS_Relationship and inject them as content item reference field values.

Feed the transformed data into XbyK via UMT's import pipeline. This is the same pattern used successfully in complex migrations.

Use the Migration Tool's custom class mapping feature (Migration.Tool.CLI config + Class Mapping) to transform source page type fields during migration and populate the new reference field with the related document IDs.

During the pages migration run, your custom mapping code queries CMS_Relationship for each page being migrated and resolves the related page GUIDs into the new XbyK reference field values.

Thanks