Bug into parent direction, if two parents available?

[michaelsjackson]

Not sure if this is a "bug" or not. Anyway, here the experiment:
Add an entry to org-brain. Then add two parents to this entry. Now visualize entry, none of them is shown in obvz. But if you add two children to this entry, both are visualized as well.

It seems obvz only collects entries in child direction but not in parent direction. Is this correct? My guess would be yes, so far.