Linked issues not fetched VIA API

[Mathi]

• I have linked the JIRA software issue in the service management project issue.
• When I try to fetch linked issue via JIRA Rest API, I can't able to fetch the linked issue in the API response. Even though I have linked JIRA software issue with it.
• But when the service management issue was linked with it, I can able to fetch the linked issue in the API response
• Below are the sample response attached for your reference.
• API that I have used to fetch the linked issue,

https://neustar.atlassian.net/rest/api/3/issue/{{issuekey}}

API Response when JIRA Software issue is linked with Service Management issue.

API Response when I linked Service Management issue with Service Management issue.

Please advice, how to fetch the linked issue in JIRA REST API when JIRA software issue is linked with JIRA Service Management issue.

Thanks,