Genetics/heredity and probability?

If a couple has four children, what is the probability that the FIRST TWO will have will have galactosemia and the second two will not? I know that galactosemia is a recessive disorder, so essentially there is a 1/4 chance that a child could get it (the parents are both heterozygous for the trait), but I do not understand how the order in which the children were born would be calculated in probability.