How Did One Family End Up With 4 Genius Kids?

Four Texas quadruplet teens were recently accepted into the Mensa Society!  Most family's don't even have one Einstein in their family but to have four.  Three of them speak Chinese and the other does sign language.  Maybe it' something about the Chinese language and how it activates different parts of the brain.  But really, what are the odds of having four in one family?  I bet they could calculate them.  

Quads All Members of Mensa: MyFoxDFW.com