Auto-change owner for dependent tickets

I have set up a queue to track requests for new or upgraded PCs. When a
ticket is created there, it creates a ticket in another queue which the
original depends on. The purpose of this is to separate correspondence
with the end user and comments re: the progress replacing the machine.

I am running into trouble changing the owner on both when someone takes
the original ticket (i.e. 7518 is the request for an upgraded PC, 7519
is the tasks required to complete. I want the owner set on both when a
tech takes 7518).

Any pointers on what I should be looking at?