I can name at least three families who had BBBG. It really is a 50% chance with each pregnancy. I'm trying to brace myself for a fourth boy, but scientifically speaking, it's 50/50. I think the fact that we are all so obsessed with gender (myself included!) that it doesn't feel possible to conceive a girl naturally after having three boys, but it is possible. In fact, that is how I finally got over the "I'm not good enough to have a girl" part of GD. I just flipped a coin three times and got all heads - that's all. It says nothing about who I am as a person or how deserving I am. It's just the luck of the draw.