# Add related customer (/docs/api-reference/customers/relationships/add-related-customer)



{/* This file was generated by Fumadocs. Do not edit this file directly. Any changes should be made by running the generation command again. */}

Add a person who shares this customer's phone number, such as a spouse, or link an existing customer. Call it when POST /v2/customers returns 409 with an existingCustomerId. A person already on the number is returned instead of duplicated, so retries are safe. The person is not the number's primary unless isPrimaryForPhone is true.

<APIPage document="&#x22;../../apps/api/openapi/specs/openapi-public.yaml&#x22;" operations="[{&#x22;path&#x22;:&#x22;/v2/customers/{id}/related&#x22;,&#x22;method&#x22;:&#x22;post&#x22;}]" />