Replicate the "Group Members(sys_user_grmember.group)" related list on Group form for a custom table

[Mudabir]

I have a custom table ( Custom 1) with two reference fields 
1. Group field ( Reference to Group table)

2. Issue  field ( Reference to a different custom table (Custom 2))

On the Group form I want to show a Related List that shows the records from Custom 1 table ( which is pretty straight forward)
I want "Edit" button on this related list. But when the "Edit" button is pressed, on the left side of the slush bucket it should show records from Custom 2 table. Just like for ""Group Members" related list, this related list shows user records on the left side of slush bucket when "Edit" is pressed.

Thanks!

[Mudabir]

@JenniferRah 
Issue resolved. Instead of creating a record in sys_m2m table, I created one in sys_collection. It works like a charm now. 
Thanks for all your inputs.