I am working on User Permissions and Limitations on the basis of Roles and Profiles in Zoho CRM.

I have created three different roles in CRM which are:

1. CEO
2. Manager (Also have sibling i.e. Manager1)
3. Agent (Also may have siblings i.e. Agent1 etc)

It will be looked in CRM like:

 

Now I have two requirements.

Requirement # 1

A record should be visible to Owner and its Parent role but not to siblings. 
Like if a record is created by Manager, it should be visible to Manager and CEO but not to Manager1, Agent and other child roles.

Requirement # 2
If a role wants to assign its record to someone else, it should be allowed to assign the record to its child role only. not to siblings and Parent Role.

Means if a record is created by Manager, and it wants to assign it to someone else. It should be allowed to assign that record to its agents, not to Manager1 and CEO. I share a screenshot here to make it more clear.

Here the record in screenshot is created by Manger and He wants to assign that record to his Child role i.e. Agent.

I want that only child role users should be shown in the list to whom we can assign record, but you can see in the screenshot that all the users are available in the list.

Requirement # 1 is almost done but I have no idea about how to complete Requirement # 2.
So please give me idea about it.

Thanks