Well considering it is a bible verse, you can misinterpret it all you like but anytime you read the bible the actual, real verse will be there. It's not a quote passed on through "word of mouth" but instead a bad interpretation of text. You can take any text from any book and twist it as you see fit and make it commonly used but it doesn't make it any less wrong of an enterpretation. Plus this particular phrase's original text is somewhat well known. I've definitely heard people correcting others for using it "incorrectly". Which begs the question, at what point do we draw the line? When the majority uses it wrong? By how much of the majority?
I read the Bible and I have taught the Bible. There are all sorts of things in the Bible that are interpreted in different ways in modern times (the one about name in vain, being one). The important thing in communication is what it means NOW to the general audience, just as words change in meaning, sometimes radically, from initial usages.
Sorry so I did some pretty deep, extensive research and as it turns out the Jewish bible it was taken from was a somewhat radical sect that did not cite anything and just expected people to believe (and believe they did. The phrase I shared above is apparently wildly popular and used by almost every category of people who preach to others) which is why there is a lot of "evidence" to show that is the original phrase, but only since the 1990s. However, the phrase did indeed originate from a phrase that means the opposite of the intentions it's used for today, "Blood is thicker than milk" a.k.a. blood brothers are closer than mom('s milk). Whether or not the way it is used today is more substantial information than the original meaning is more of a philosophical question than it is grammatical rule, especially in this case where water has no meaning so who cares if blood is thicker. I will say that original meaning has more weight to me when a proverb is used as evidence for action (as in this case with the mother) but I can understand why others wouldn't.
I expected as much. I'm VERY familiar with the Bible and I did not recall any such saying. The covenant relationship is considered primary by many believers (ie, we call each other "household of faith" or "people of the covenant"). Like marriage--two non-relatives (generally) will become relatives. Become "blood" by the covenanting in marriage.
However, for hundreds of years, we use "blood/water" not "blood/milk" etc. It's very common saying, after all. Thanks for looking into it. Until I see an actual scholarly citation of a millenial old use of it to mean what this "sect" says, I ain't buying it as being the saying we use today.
I laughed pretty hard at this
http://www.mangago.zone/read-manga/princess_s_happily_ever_after_marriage/nto/to_chapter-46/4/
Because "blood is thicker than water" is just shortened slang for "the blood of the covenant is thicker than the water of the womb"
Aka: Those you bleed for are stronger connections than those you share womb water with (family)