I've got light brown hair, and my wife has naturally slightly darker brown.  I wonder if people tend to pair with people with the same hair color.
I'm not so sure about that. I have brown hair, but hubby has black hair. 
I guess it's a silly thought, but sometimes I have them :P  Fun fact, your husband has more hair follicles because of their black hair?
Really? I didn't know that. I guess that explains why his hair is much thicker then mine. 
Yeah, it would be that.  It's probably one of his defining characteristics :P