This example has two Job Chains.
Each job chain having its own set of jobs as shown below.
Now the Job21 on Job_Chain2 is dependent on completion of 'Job_Chain1' and 'Job_12' (There may be scenarios where Job12 could be manually skipped).
How it works:
A sync job is located at the end of job chain1 and at the beginning of job chain 2.
Job12 has a command on exit code=success which will create an order for job chain2. But the order will not start, as the first step is a sync and the corresponding sync in job chain1 will release the order for job chain2.
You can download the source for this example from here.