  We work out the effects of hypercritical accretion, which transfers mass from
the secondary to the primary (first-born) neutron star (NS) in a binary,
showing that the mass of the primary would end up 0.6 M_sun greater than the
secondary NS in contradiction with the very nearly equal masses of the two NS's
in binaries measured to date. We discuss that the primary NS evolves into a
low-mass black-hole (LMBH) due to the hypercritical accretion. Using a flat
distribution in the mass ratio q (q = M_secondary/M_primary), we calculated a
ratio of LMBH-NS and NS-NS systems to be 5, in rough agreement with
Pinsonneault and Stanek (2006). These authors emphasize the importance of
"twins", which we discuss. The two NS's in the twins would be close in mass and
further increase the number of mergings.
