I tend to think that the idea of "golden child" is in the eye/mind of a beholder who is not the parent of the child/children in question. Maybe it's one sibling who thinks another is "the golden child". Maybe it's someone who, for some reason, always imagined himself to be "the golden child". Maybe it's another family member who doesn't understand/see why one or another (or both) parents behave one or another way toward/about one child versus others.
It's not all people who don't know/see/understand some of the valid realities of things( like different circumstances as different kids reach different ages, spacing, etc. ), There are parents who "set up" the "Golden Child thing" without realizing they're doing it; but I think in such cases it's more a matter of a flaw/mistake a parent is making (which, to me, isn't so much a matter of the child being "a golden child" as it is with something like a flaw in the parent's communication and/or with something like being happier with a child who tells the parent what he wants to hear because the parent hasn't let the child know it's more important to be free to say what he really thinks/feels than what the parent wants him him to say).
To me, though, the "Golden Child" thing is generally putting a label (essentially a make-believe one) on the child; and, whether it's a matter of non-parents imagining it out of ignorance, or parents "setting it up"; the child in question is not the one who should be labeled.
In other words, I just think (regardless of the reason/cause) for the appearance of the "Golden Child thing", anyone who is even willing to think in terms of using that label (on himself or others) needs to gain a better understanding of the dynamics (that is if it's even his business at all). And, if it's not his business at all then at least recognize that a label based on (essentially) "nothingness"/thin air amounts to make-believe (regardless of who it is he thinks deserves that label).
There are healthier ways to describe an apparent "Golden Child" situation. To me, if the appearance of one exists then it's even more important to discuss it in the healthiest terms (and ones of substance, rather than essentially "thin air").
I'm not directing this at poster of this question, but at anyone who thinks in terms of the "Golden Child" label. There's children who are treasured/valued, which is a different thing (and not a label). "Golden Child" is a whole other thing.