Egalitarian relationships are those in which partners equally share all benefits, burdens and responsibilities. Egalitarian relationships go against the societal norm due to the lack of traditional gender roles. Friends, siblings or work colleagues also can be in egalitarian-type relationships even though they are not partners.
Lori Gottlieb suggests, in her NYTimes.com article "Does a More Equal Marriage Mean Less Sex," that "the very qualities that lead to greater emotional satisfaction in peer (egalitarian) marriages may be having an unexpected negative impact on these couples' sex lives."
She came to this conclusion based of the findings of a study called "Egalitarianism, Housework and Sexual Frequency in Marriage." This study originated to argue that egalitarian relationships should be the norm because of the positive benefits couples experience. However, the findings backfired as the results came back that when men took on more feminine roles, the couples had less sex. In relationships where men took on more traditionally masculine roles, their wives reported greater sexual satisfaction.
Although these findings are interesting, they do not apply to all people and relationships. Just as with all relationship types and behaviors, egalitarian relationships work when the partners agree that this style fits for both of them.