What is the underlined idiom
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<span>True, after getting a marriage in a family which results expansion of the members. It is not by the way of adding two people but by other relatives belong to the couple also added as a family. Or also a family can include people by its own choice because a family can afford an orphan or like these people as a choice and it depends on the attitude of the particular family.</span>
It is a a trait that helps a creature survive in a particular environment.
