I remember asking my dad when I was little about the concept of blood brothers. I'd probably seen it in some movie where the characters prick their fingers or hands and then mesh their little drops of blood together and proudly declare, "We are now blood brothers!" (Or blood sisters, whichever.) I was confused about the ramifications of this.
So, I decided I'd question my dad about it. I asked, "If a white guy and a black guy became blood brothers, does that mean that when they have kids, the black guy's kids will be part white and the white guy's kids will be part black?" I remember him laughing, and saying that he could understand why I'd think that, but no, they wouldn't. He then tried to explain genetics and DNA to me, my very first scientific explanation. I totally didn't understand it.
I've never had a very scientific mind.