Unable to get values for nested fields through API (JSM)


I’ve been working on an integration of JSM (creating issues based on request type) with another SaaS application and I’ve been encountering an issue where the nest field values are not being shown in the API response.

The above screenshot is taken from the customer portal of JSM where if I choose different values for the “Brand” field, a set of values will be reflected in the nested/children fields underneath it (priority & labels).
However, if I try to view the API response with a value available to the “brand” field… the children array is empty. Is there a way to get the values for the nest fields through APIs?

JSM Details: “version”: “5.4.3-REL-0001”,
“platformVersion”: “9.4.3”,

The JSM is an On-Premises instance.