JQL - issues with parent belonging to particular epic

Question

I need to find all the sub-tasks in my project that have parent in its turn belonging to the particular epic. Unfortunately sub-tasks do not have epic field, otherwise it would be easy.

Thus, the tree-structure is like:
Epic --> Task --> Sub-task that I need to find.

Is it possible without plug-ins?

Julz_tb6fq2 · Accepted Answer

Luckily I've found it myself, perhaps it might help anyone else.

issuetype = Sub-task AND issuekey in childIssuesOf(<epic_link>)