Yes, that would place both motorcycles in the container along with the rider. Its like an unbreakable chain.
What you are wanting is something like the Object Pairer from Construct Classic. It could pair objects together for picking without the creation/destruction issues. I think its on the todo list.
The work around for now is storing the corresponding objects uid in an instance variable.
You can also try using IID, but that can get messy.
Or are you confused by the fact that you can not use one object as a parent if the other objects are already in a container?
I know I am.