The Wolfram|Alpha blog shows examples, starting of with "my cousin just had a son, what relationship is the son to me?" To find out, simply enter: "Cousin's son" into the (Answer: he is my first cousin once removed.) Wolfram|Alpha even displays the relationship visually. You can then go on to more complex relationships. For example, try "my cousin's granddaughter."
Wolfram|Alpha can even display complex connections, such as the one described in the title above: "Cousin's Cousin's Niece's Grandfather." Actually, the two are not related at all but Wolfram|Alpha draws the diagram anyway and then states, "blood relationship fraction: 0%" which means they are not blood relatives at all.
You can read more at http://blog.wolframalpha.com/2010/06/21/my-cousins-cousins-nieces-grandfather-said-to-just-ask-wolframalpha/ and then try entering some relationships yourself at http://www.wolframalpha.com