Afaik with the celts those were the worldly male representives(sons) of the female godess, like danu and dagda. But i got that info only out of 1 book and can't find much online.And who tf knows what some of those extinct races believed their gods to look like.
The first three depictions were done by "older white men" many decades (or centuries) later.
Are they just wishful thinking (homoerotic fantasys?)?