Hi all,
Though I do not post frequently, I've watch the peregrines nearly everyday for the last two years (the joy of being a self-employed computer person).
One thing that I have noted is that Princess and Trey do not favour one chick over another - it's all about survival. At feeding time you can rest assured that everyone will receive a portion of the meal. If one chick seems to get less at one meal they are typically topped up at the next.
The easiest way to ascertain "fairness" is to look at the chicks' growth. They are proportional to one another. There are, and will be, some variations due to birth order and whether they are male or female, but Trey and Princess are diligent in attending to their whole brood.