selection of specific manager from the incumbents present on parent position

Summary:

Hi All

We have a use case where Parent Position has more than one incumbent and parent position has 10 child positions . So we would like to check if we can share 5 child positions to one parent position incumbent as line manager and other 5 child positions to another incumbent of parent position as line manager . And if it is possible how can we achieve it . As I see if we have more than one incumbent on parent position a person with longest tenure will become manager of all child positions .

Please help with this information if our use case is achievable .