i would think that by drinking the urine of someone other than yourself, you would be missing out on some of the biofeedback benefits of ut- your own urine contains information about the state of your health that by ingesting will help your body to tune itself. so i dont think it is really as much a question of same sex/opposite sex, quite so much as that you stand the most to gain by using your own urine rather than that of anyone else--
maybe there is something to that though- would it be better to drink your brother in law's urine or your wife's?