There are several ways you might do this, which is part of the reason we ask you to show your own ideas.
One is to first find the probability that neither kid chosen is a girl (that is, two boys are chosen); that's easier than doing it directly. This requires knowing about "and" and "not" in probability.
Another is to find the number of ways to choose 2 kids from the 13, and the number of ways to choose 2 kids, at least one of whom is a girl. Then use the definition of probability. This requires some knowledge of permutations and combinations.
Does either of those sound like something you can do? Give it a try.