It means that blood relation guarantees nothing — that a son can forfeit every claim to the word family by his conduct, no matter how much DNA he shares.

But it also means that family is available to be built, and rebuilt, and chosen, by anyone willing to do the building — that the bond is not locked by biology but open to be earned, which means no one is ever simply stuck with the family they were born into, for better or worse.

My father proved that blood entitles you to nothing.

I learned, in the same month, that love entitles you to everything.