I have signed no contracts or agreements whose existence I cannot mention.
They thought they found in numbers, more than in fire, earth, or water, many resemblances to things which are and become; thus such and such an attribute of numbers is justice, another is soul and mind, another is opportunity, and so on; and again they saw in numbers the attributes and ratios of the musical scales. Since, then, all other things seemed in their whole nature to be assimilated to numbers, while numbers seemed to be the first things in the whole of nature, they supposed the elements of numbers to be the elements of all things, and the whole heaven to be a musical scale and a number.
It is not clear to me this behavior is particularly christian, nor its inverse particularly a-christian. Nor even that Socrates/Plato would say Euthyphro has even come to a wrong conclusion! Indeed, in The Republic, Plato argues his perfect society would eliminate the family as a unit, so he clearly does not feel it particularly Good to treat your family different simply because they’re your family. He generally treats the institution as a competing loyalty against the Good.
Unless by “proto-Christian” you simply mean coming to occasionally correct, but mostly incorrect poorly-thought-out conclusions. If that is what you mean, then I would again argue that Plato and Socrates beat you to it, and indeed this particular mode of behavior is a human universal.
More generally, you are again falling for the Nietzscheian reading of history, which frames Christianity as much more of a novel moral innovation than it in fact was. I have argued to you previously about this the last time I noticed you peddling this particular (mis)reading of history.