Coordinating reverse flight itineraries

I sometimes book flights where I travel from A to B, to pick some people up from B that then follow me back to A. However, I have found that it is extremely difficult to book the same flight from B to A for the whole party, since it is two separate bookings.

For example today, I booked GVA-HND and back for one, and then HND-GVA and back for the other party, trying to coordinate the flights on the HND-GVA part. For the party starting in HND, I easily found various itineraries with China Eastern. But, when I on the same site search for GVA-HND, it refuses to show any China Eastern flights at all.

In the end I had to search over 20 different websites, until I finally found one that managed to locate these elusive China Eastern flights for the GVA-HND booking. I used both carrier and flight departure time filters to find the correct flights, yet it failed on most sites. And of course, all that searching at once from one single computer, meant that the prices exploded in the mean time (I had to change date, use a private browser and VPN to partially reset the price increase).

The flights evidently exist, so why should it be so difficult to reverse the routes?

Is there a good way of doing this kind of double and reverse bookings such that the common part is synchronized? Does any website allow doing it in one single booking?