The Scots/Irish clarsach (medieval wire-string harp) of yore had the two central strings tuned to b, and were referred to as the 'two sisters'. I have a couple of theories as to why this should be. 1) one of them was b flat - necessary for medieval music theory and practice, 2) most clarsairs were blind, so two 'b's helped provide a position guide. Both theories have been rejected by clarsach researchers, but no alternative theory has been advanced.
Rob -- To get on or off this list see list information at http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html