I also sent the picture of #3 (right) standing near to one of the twins (left).
There is an outside chance of these being smallish formels; but with all the food they had, that's not probable. And the strong flight of the first-to-fledge hawk affirms the healthy diet.
Fledging sequence is not necessarily in hatch sequence. Too many fledge-promoting variables---few of which we know much about. Stochastic. Chance."
So there we have it - #3 is almost certainly a tiercel, and the twins are definitely a formel and likely another tiercel.