I am working on the BIg picture Gantt chart

[Iram Masood]

While creating the Gantt chart i can see few of my tasks are correctly mapped with my Epics but few are directly mapped with initiative wheras they should also come under epics.Iam unable to find the resolution.I check all filters and queries everything is similar. 

[Marcin Geb _SoftwarePlant_]

Hello Iram,

It sounds to me as if you didn't have structure builders in place. I'd begin in a BigPicture's program configuration > Tasks > Task structure, as evident in the screenshot below.

Now, how to use structure builders? Typically you'll have up to three of them enabled. For instance, the Parent-Child Link, evident below, is responsible for the first, highest level of the Gantt chart's hierarchy.

You can add your custom issue links in Jira administration > Issues > Issue linking, and those newly added links should become available as BigPicture structure builders.