Yup, its true. More than likely your Grandma had sex before marrying your Grandpa, although it was probably with your Grandpa that this happened. I know this to be true in my family - even though it isn't something that is talked about. I blame TV and movies for making us think things were different back then. People were just more apt to get married, cover it up and take responsibility back then.
I LOVE the Discovery Channel and the Science Channel as well as the History Channel. With that said, do we really need this information? Unless you can give the sperm a cold to keep the little guy from smelling, what good does it do to know this creepy fact?