While we're on the subject of Ibeji figures and twins, I thought I'd
share a pic of a heavily used Lega "twin" mask that was just collected
in the Kalima district of the DRC: (http://ph.groups.yahoo.com/group/African_Arts/photos/view/d009?b=1)
I've posted photos in an album called "Lega "twin" mask, etc.":
These masks are very rare and are sought out by couples after the birth of twins to propitiate the "twin" spirit to help ensure the children stay healthy. Not surprisingly, given the extra resources twins require both in and ex utero, it is apparantly common for one child to be less healthy and possibly die. As such, it appears to be a fairly common practice in sub saharan religions to honor and appease the twin spirit to help ensure their health.
I've also included photos of a fine Lega muminia mask: http://ph.groups.yahoo.com/group/African_Arts/photos/view/d009?b=2
Biebuyk states that these masks are an older form among the Lega and are used for a variety of ceremonies of the bwami society. They are usually possessed by specific families or lineages and are passed on through generations as evidence of the "pedigree" of that family (for want of a better word).
The final pic is of a Luba-like mask that is actually Azande
(the one in the middle), which I'm told are very rare:
Anyway, I'm in the process of trying to acquire these from my friend, but I thought I'd share them given their rarity and the Ibeji discussion. If anyone has any additional info on them, I'd welcome any thoughts.