Some press are quoting the infamous sources today saying that The Queen is sensitive to Prince Harry's situation as the second sone to Prince charles having seen the way Princess Margaret struggled with this situation. This has been written about a lot but who actually knows what the Queen thinks but it is easy to understand why this is could be difficult to cope with.
As a child the second child is second in line for whatever title, in H's (an PA) case Prince of Wales and heir to the throne. Everyone treats you as befits the second in line.
As time goes on the importance of the first in line increases and will continue to increase as, in due course, those ahead of them in the succession age and eventually pass away. For the second in line though their importance steadily decreases and, as the first in line has children of their own they get pushed further and further down the pecking order.
Some, like Princess Anne seem to take this in their stride. (I would have thought she would have more reason to feel aggrieved having been second in line until Andrew and then Edward were born but she, on the face of it at least, seems to have just got on with it.
By some accounts Princess Margaret and Prince Andrew both found this difficult to cope with and insisted on what they considered to be their due in terms of deference etc.
Perhaps H, despite the happy go lucky personality we were used to seeing in public, found this more difficult to take that we would have thought.
My long winded point is that it isn't just the difference in "importance" or the final destination but that the gap gets wider and wider as the years go on.
As the preparations are made for the time when PC will take over from HMQ, the gap between PH and PW has been and will get wider and wider.
Sorry for the obvious points. Just working it out for myself