Hey, you must be very excited about taking your first flight ever, I remember when it was my time, and I could not stop looking out of the window when I was finally aboard.

I am really sorry having to break the bad news for you though: If you miss your outbound flight and do not even change and then fly the outbound flight after the initial departure date, your return leg will get voided. There is no chance that CX will let you board the return flight without you having taken the outbound first, no matter what your brother has done or not. The CX website does not always reflect all the status quo of all bookings in real time, so I would not rely on it to make decisions.

So you will probably have two options now:

1) Call the OTA and ask if they can help rebook the FRA-HKG-DPS sectors to a later date, take that flight, and then you will have no problems getting on the return flights. Your OTA will most likely charge you a no-show fee in addition to a change fee, all provided that your ticket contains a no-show option that allows you to rebook after the original departure date.

2) Buy a new ticket DPS-FRA and forget about your old CX ticket.

Hope this helps!