I tried to recreate the relationship you described in a test tree, and I could not get the the tree to display in the way I expected it to either. So, I don't think you're doing anything wrong, or that there is a setting that you're not aware of. I think the software is doing something a little odd in this case.
Having said that, I do not expect it to show the multiple relationships at the same time. But I would think it would be possible to show the ancestors of either side of that relationship when you click on someone from that side of the tree, and I don't think it is doing that now.
You'll probably have to use the send feedback button to ask for this feature. I'm adding this as a comment instead of an answer on the off chance that someone has a better understanding of what's going on.