Here is a list of issues Geni is aware of and working on correcting:
Map Geocoding Issues
Currently there is no way to show multiple births (Twins, Triplets, etc.) on Geni in the birth order field.
Noah replied in http://forum.geni.com/topic.php?id=2109&replies=12#post-13771 forum thread] "Currently we do not have any special indication for twins or other multiple births. Obviously as a less than usual family relationship, multiple births are something we should expect to have full support for in the future."