Thanks everyone. So, here's a bit of an update: I did talk to both of them. They both stated that this is a "them" problem and I'm not the issue. My introduction into the mix has created the need for some additional pieces of communication between them - particularly having to do with time. She was feeling somewhat dismissed and acted out.
I still have an underlying issue. Chiefly, that although they both state that they don't "do hierarchical poly", in reality, that's more or less what they have. I still feel as though I need to get approval from her to spend time with him. This may be more perception than reality on my part, but I'm feeling somewhat like a widget at the moment.