Hi @Geelong,
Yes, eazyBI allows creating Issue hierarchies based on issue links. It is essential, though, that each child in the B and C projects has only one parent in the A project.
Here is a good explanation from my colleague about building additional Issue hierarchies: How to create an additional issue hierarchy.
Another option is to create additional issue link dimensions where there is an option for multiple-to-multiple links, see Import issue links as dimension.
Please try this with your data, and if you have any further questions, probably best to write details about your setup to support@eazybi.com.
Lauma / support@eazybi.com