Is this true?... About humans...?

The only thing I can think of is that people's scent is an indicator of there major histocombatibility complex (MHC). The MHC plays an important role in the immune system. Related people have similar MHCs. There was a study done with college aged girls where they had them sniff tee shirts used by males how had just exercised. the women preferred the shirts of males who had very different very different MHCs.This could be explained by the fact that offspring would benefit from having a diverse MHC that would protect them against a wide set of diseases. I would all also help explain inbreeding avoidance. Having very similar MHCs would have the opposite effect