Clustering for social/complex networks

Hi group,

Here is another clustering question.  Is there
anything available in R that I can cluster groups with
overlaps?  It looks like a Venn Diagram with two or
more circles overlapping one another.  

I realize that Hierarchical Clustering (hclust in
Stats) only group individuals into distinct groups. 
My scenario is I have to group Physicians that each of
them may belong to more than one group.  That reflects
the complexity of relationhip, something analogous to
Social Network.  

Thanks!

kel