I found three different images showing the complex network of ownership between the automotive companies. Three different attempts at making these complex relationships easier to understand. This first one is a scan from a magazine, but I can't find any reference to which actual magazine it came from. Charted out like a subway map, it's pretty easy to follow.

This next one from Too Many Cars is charted like a family tree, or a mind map. It's the easiest the follow, but probably the least aesthetically pleasing. Online the image is broken into smaller pictures so you can zoom closer, but is also available as a large poster in PNG or PDF formats. The data for this one is from 2006, and is the most current of the three.

This last graphic claims to show the ownership mix in the auto industry as a form of bubble chart, but I can't find any date or source data link. I think the bubble sizes represent something, like size of the company or ownership, but I can't tell. So I can't tell how accurate this is. The image is on Tinypic.