3rd precedence graph is correct.
What I think, we can solve it by checking the flow of the execution. First, after S1 , fork is done and new process's address S3. so two arrows from S1 (i.e S3;new process address , S2;normal execution) . Similarly proceed with other forks. At DEF we can see S5,S4,S2 can reach. So, these processes are combined.
Please correct me if it's wrong.