Given that a proportion p parents are of some particular haplotype, the probability that the selected number X(t + 1) of l children out of an effective population of size N is P(X(t+1)=l)=(Nl)pl(1−p)N−l. Given that j out of N parents are of the haplotype of interest, then p = j/N. Therefore, the probability of finding l children of the haplotype of interest given j parents is P(X(t+1)=l|X(t)=j)=(Nl)(jN)l(1−jN)N−l.