Learn English – Word to describe one who loves friends more than family

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Is there a word to describe someone who loves his friends more than his family?

For example, my brother is a sort of person who seems to be only interested in his friends (not me nor the rest of the family). I'm looking for any words and/or idioms to describe my brother.

Best Answer

OP's brother is exhibiting extrafamilial orientation - normal behaviour for young adults of both sexes as they approach the age at which they will leave the parental "nest".