1. Parent case will have 2 or 3 child cases at any point of time.
2. Same operator should not be working on more than one child case.
3. Pull routing is used, i.e. assigments are pulled from workbaskets when user clicks on "Get Next Work".
I am thinking about the following approach:
1. Propogate child case1 owner details to parent case and store them on parent case.
2. When child case 2 assignment is being pulled, compare with the data at parent case by customizing get next work criteria.
Please let me know if there is any better way to do it.
I think you're taking the correct approach. You're going to need to customize get next work in order to have it filter out cases that are otherwise appropriate if the owner already has one of the siblings.