Multiple relationships for multiple node types

I setup a view with a node type that needed a relationship to work properly, which is working fine. I now want to add another node type to the view (i.e. tick two boxes in the node type filter) so that nodes of both types are displayed, however the second node type also requires a relationship...

How do I setup two relationships for two different node types?
You have to select which relationship to use for each field, but in having two relationship, I can't choose both...