  We present new analysis of O-C diagrams variations of three Algol-type
eclipsing binary stars AD And, TW Cas and IV Cas. We have used all published
minima times (including visual and photographic) as well as new determined ones
from our and SuperWasp observations. We determined orbital parameters of the
3rd bodies in the systems with statistically significant errors, using our code
based on genetic algorithms and Markov Chain Monte Carlo simulation. We
confirmed multiple nature of AD And and triple-star model of TW Cas and we
proposed quadruple-star model of IV Cas.
