I don't know to many young adult's getting married until they are in their late twenties or early thirties today.
We do not know if the Prince had a real fall out with Kate or just hear say. I believe Prince William and Kate were under a lot of pressure earlier from the press and not being committed to each other officially. I believe they did spilt up publically for a few weeks or about two months and then took it easy getting back with each other. But sometimes spilting up brings people closer or breaks them apart. I think in this situation it brought them together. This is only my thoughts on this relationship.