Validate child issues are closed before parent issue is moving to completed status

[Geethanjali S J]

Hi, 

We are using jira cloud. 

I think so we have build in workflow condition for this for sub tasks but our hierarchy is

Initiative

MBI, Sub Service

Epic

We would like to check each child issue types to be closed/done before the parent issue is closed

Here we have MBI as parent of an Epic

We need to prevent the MBI from being able to transition to complete unless all of its children are either in done or closed status. 

Please anyone can help me with this. 

Thanks,

Geethanjali.