two separate clock tree from one point

This looks like a special case. In order to answer your query, it would be good to understand the exact requirements.

What are the design constraints that's prompting you to build 2 separate clock trees from one point?

Regards

Rajesh

 Hi,

the clock tree synthesizer balance clock tree by first balancing the subtree downstreem of each multiplxer 

and then representing the mux and subtree with seprate macro for each mux input, each macro represent path delay from coresponding mux input to sinks receiving clock signal input via subtree.

when the clock tree include cross over point the macro split into seperate tree for each clock signal.

Mitesh