Hello. Thank you for contacting the Toolset support.
Well - I would like to know that are you using new post relationships that is made available with latest Types plugin version 3.0 or have you migrated your legacy (old) relationship created using Types plugin before version 3.0?
What is your parent post type and child post types? Could you please send me screenshot of page:
=> Toolset => Relationships
my site wasn't ready when the Types 3.0 was released and I decided to set my website up from scratch, using only the newest releases of the Toolset software, so I didn't migrate anything.
Glad to know that the solution I shared works for you.
May I kindly ask you to open a new ticket with your each new question. This will help other users searching on the forum as well help us to write correct ticket resolution summery.
You may create a new ticket and feel free to assign it to me.