Those fledged and fledging

The merlins story is a late one this year due to the fact that Spike and Thor had to move their nest from one very open and unstable site to the present fir tree which is the polar opposite of the former. In fact, up until the last couple of weeks, there was a question whether there would be a nest at all because it could not be seen. After careful observation of the parents' behaviors (pretty well known now from the past two years practice), we figured out that, indeed, there was a nest and eggs and, after a bit of time, hatchlings were being fed. The last 2 weeks have led the birders to believe that there are 3 fledgees (only because that's all that can be seen from hours of observation by scopes) but there may be more. Time will tell.
So, save for the lateness, all is pretty normal except for the fact that there are, a few people have noted, 5 adults present around the nest. Twice, we have seen 4 adults. Two are identifiable as the parents, Spike and Thor, and the other two are unknown. A couple of people have witnessed yet another single bird, a "rogue" merlin joining the group. That is the important part of the last sentence: the group. From what we have all seen and noted, this is a group. There are no "enemies" as there is no defensive posture or threat in evidence when these 2 or three other birds are there. In fact, we saw that they were flying quite close to the new nest without being "buzzed" by Mom or Dad. So, we can only deduce that the "extras" are offspring from previous years, older brothers and sisters, who have not "left the nest".
There was a report on the internet this week about this in the human population. Large numbers of recent college graduates are returning to their parents' homes because they cannot find jobs or cannot afford to live on their own. Perhaps they just don't want to live elsewhere. Who knows? The phenomenon is large enough to be noticed and notable whatever it's cause. Could our young adult birds be similarly afflicted? They are a little old to be hanging around the nest. Perhaps they just cannot find enough food to sustain their own nests. Again, who knows? It is a very interesting proposition to ponder.