How to change the speed of duplicated rig animation

If I am using the same animation for two separate characters, how can I edit (slow down the walking cycle) of one of the rigs? When I try to select the rig in the timeline it selects both rigs. I created a new animation and tried to edit the animation there but it just changes the original timeline as well. How can I unlink/separate the two rigs in the same animation using the same/duplicated animation?