Very nice family shot! As to your questions, not all the eggs in a clutch hatch at the same time, and not all the young progress at the same rate. The early hatchers get more food and attention to start because there are only a couple of babies to take care of. The ones that hatch later have to compete for the food and are "behind the curve" in the amount of nutrition they get. (although the parents are very good about feeding all the babies).
The wing fluffing bird is the male. He could be doing a couple of things, it depends on how close you were, if he held the wings that way, etc. If you were close to them, and he held that pose for more than a couple of seconds, then he was fluffing up to look threatening. He could also have been stretching or re-aligning his feathers if he did not stay in that position for more than a few seconds.