Nested documents and many-many relation

[Sathyakumar Seshachalam]

Hi,

Am trying to investigate the possibility of using Block Join query parser in a 
many-to-many relation scenario.
Observation is that when a document is added as a child to more than one parent 
document (I use Solrj to do this), I seem to get two copies of the child 
document. Can this be avoided ? Is this per design ?
Are there are articles talking about ways to model a many-to-many relationship 
(even if its a hacky solution).