  We collect the data of twin kilohertz quasi-periodic oscillations (kHz QPOs)
published before 2012 from 26 neutron star (NS) low-mass X-ray binary (LMXB)
sources, then we analyze the centroid frequency (\nu) distribution of twin kHz
QPOs (lower frequency \nu_1 and upper frequency \nu_2) both for Atoll and Z
sources. For the data without shift-and-add, we find that Atoll and Z sources
show the different distributions of \nu_1, \nu_2 and \nu_2/\nu_1, but the same
distribution of \Delta\nu (difference of twin kHz QPOs), which indicates that
twin kHz QPOs may share the common properties of LXMBs and have the same
physical origins. The distribution of \Delta\nu is quite different from
constant value, so is \nu_2/\nu_1 from constant ratio. The weighted mean values
and maxima of \nu_1 and \nu_2 in Atoll sources are slightly higher than those
in Z sources. We also find that shift-and-add technique can reconstruct the
distribution of \nu_1 and \Delta\nu. The K-S test results of \nu_1 and
\Delta\nu between Atoll and Z sources from data with shift-and-add are quite
different from those without it, and we think that this may be caused by the
selection biases of the sample. We also study the properties of the quality
factor (Q) and the root-mean-squared (rms) amplitude of 4U 0614+09 with the
data from the two observational methods, but the errors are too big to make a
robust conclusion. The NS spin frequency (\nu_s) distribution of 28 NS-LMXBs
show a bigger mean value (about 408Hz) than that (about 281 Hz) of the radio
binary millisecond pulsars (MSPs), which may be due to the lack of the spin
detections from Z sources (systematically lower than 281 Hz). Furthermore, on
the relations between the kHz QPOs and NS spin frequency \nu_s, we find the
approximate correlations of the mean values of \Delta\nu with NS spin and its
half, respectively.
