How to Relate Inbound Msg w/ BPM msgs?

I send an asynch message to XI and it goes through BPM then to a sender channel. In the monitor, it has:

-Line1 for Inbound = AENGINE & Outbound = PE

-Line2 for Inbound = PE & Outbound = AENGINE

Each of these lines have a different message ID. My question is how can I relate Line1 and Line2 together to know that they are same message sent from sender?