So I am using http://bl.ocks.org/mbostock/4339083 to create a collapsible tree and it works great.
Now the thing is I have some nodes which have the same children, so I want to know if there is any way to visualize the graph in such a way that both the parents expand to the same child?
So basically when you expand the node of a parent it should automatically expand the node of the other parent leading to the same common child, is this possible with any graph?
From your description, I gather you need to visualize directed acyclic graph, or DAG.
Tree is:
DAG is:
And, no, unfortunately, D3 tree and cluster layouts simply don't support that kind of graphs. Their internal algorithms assume that the data structure is strictly a tree.
However, there are some options. Please see these five related questions for possible approaches:
d3 tree - parents having same children
How to layout a non-tree hierarchy with D3
d3.js tree nodes with same parents
Layered graphs in d3.js
JS library for displaying direct acyclic graphs (DAGs)