Does anyone have any opinion as to what the best routing would be for this two different pairings:

SAN-EZE-RIO-SAN
and
JFK-EZE-RIO-JFK

my brother and I are attempting to meet up in buenos aires and then travel on to Rio...is it easier for him to meet me in buenos aires or MIA or DFW?

Also, on the middle leg, which partner is the EZE- RIO leg most likely to be with?