the fourth one is the one you won't see, even though you don't know them and have no idea what they went through to join up.
The fourth option is that they were inevitably going to join the military (that happens in plenty of families) they both wanted to fly and they both had to meet the entry criteria (medical, academic and selection tests), then they both worked hard during training and met the same or higher standards than their course-mates.
However, melmoth, you seem to know better
hope you are wearing your tinfoil hat so the security services can't spy on you for thinking anti-royal thoughts - it is all part of a conspiracy isn't it?
That's actually the first option crab, but hey ho.