The blood of the covenant is thicker than the water of the womb.
Sometimes you relationship with your FOC is stronger and better, because it is not built on genetic predisposition but rather it is a bond that you intentionally create.
Writing in the 1990s and 2000s, author Albert Jack[18] and Messianic minister Richard Pustelniak,[19] claim that the original meaning of the expression was that the ties between people who have made a blood covenant (or have shed blood together in battle) were stronger than ties formed by "the water of the womb", thus "The blood of the covenant is thicker than the water of the womb". Neither of the authors cites any sources to support his claim.[18][19]
Well... one cannot choose family for one is always bound to them by biology. Does that matter? No. One's life is more than that. One can leave family in the dust, a choice many of Adam's targets had to make to continue living, while others never even got to make that choice. Either way, equating (and let's be frank: most often elevating) yesterday's "hero" to family status certainly is a choice.
In this spirit: "Here's a nickel kid, buy yourself a better eulogy."
No, that's your own personal interpretation, perhaps from your own culture. For many other people, "like family" can mean "like that crazy uncle that we try to avoid as much as possible, but we can't easily keep him away from family reunions because grandma insists on inviting him, so we just try to ignore him then".
The idiomatic use is a much higher standard than literal family - members of the same family can hate each other.
As jchallis used the idiomatic term in the latter, more literal sense, I can understand people getting confused.