  We consider the evolution of sub-horizon-sized black holes which are formed
during the high energy phase of the braneworld scenario. These black holes are
long-lived due to modified evaporation and accretion of radiation during the
radiation dominated era. We argue that an initial mass difference between any
two neighbouring black holes is always amplified because of their exchange of
energy with the surrounding radiation. We present a scheme of binary formation
based on mass differences suggesting that such a scenario could lead to
binaries with observable signatures.
